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DOE OSTI2020

Materials Data on Mg(NiO2)2 by Materials Project

Mg(NiO2)2 is Spinel-like structured and crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are eight inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine NiO6 octahedra. The corner-sharing octahedra tilt angles range from 54–63°. There are a spread of Mg–O bond distances ranging from 1.96–2.00 Å. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three MgO4 tetrahedra, corners with three NiO4 tetrahedra, and edges with six NiO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.03–2.06 Å. In the third Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine NiO6 octahedra. The corner-sharing octahedra tilt angles range from 56–62°. There are a spread of Mg–O bond distances ranging from 1.96–2.00 Å. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four NiO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five NiO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.02–2.06 Å. In the fifth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six NiO4 tetrahedra, edges with two MgO6 octahedra, and edges with four equivalent NiO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.03–2.07 Å. In the sixth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six NiO4 tetrahedra, edges with two MgO6 octahedra, and edges with four NiO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.04–2.08 Å. In the seventh Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with five NiO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five NiO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.02–2.07 Å. In the eighth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six NiO4 tetrahedra, edges with two MgO6 octahedra, and edges with four NiO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.02–2.07 Å. There are twelve inequivalent Ni3+ sites. In the first Ni3+ site, Ni3+ is bonded to six O2- atoms to form NiO6 octahedra that share corners with three MgO4 tetrahedra, corners with three NiO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four NiO6 octahedra. There are a spread of Ni–O bond distances ranging from 1.90–2.06 Å. In the second Ni3+ site, Ni3+ is bonded to six O2- atoms to form NiO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent NiO4 tetrahedra, edges with two MgO6 octahedra, and edges with four NiO6 octahedra. There are a spread of Ni–O bond distances ranging from 1.91–2.06 Å. In the third Ni3+ site, Ni3+ is bonded to four O2- atoms to form NiO4 tetrahedra that share corners with six MgO6 octahedra and corners with six NiO6 octahedra. The corner-sharing octahedra tilt angles range from 54–59°. There is two shorter (1.88 Å) and two longer (1.90 Å) Ni–O bond length. In the fourth Ni3+ site, Ni3+ is bonded to six O2- atoms to form NiO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four NiO4 tetrahedra, edges with three MgO6 octahedra, and edges with three NiO6 octahedra. There are a spread of Ni–O bond distances ranging from 1.87–2.02 Å. In the fifth Ni3+ site, Ni3+ is bonded to four O2- atoms to form NiO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine NiO6 octahedra. The corner-sharing octahedra tilt angles range from 55–61°. There are a spread of Ni–O bond distances ranging from 1.89–1.94 Å. In the sixth Ni3+ site, Ni3+ is bonded to four O2- atoms to form NiO4 tetrahedra that share corners with six MgO6 octahedra and corners with six NiO6 octahedra. The corner-sharing octahedra tilt angles range from 53–59°. There are a spread of Ni–O bond distances ranging from 1.83–1.88 Å. In the seventh Ni3+ site, Ni3+ is bonded to six O2- atoms to form NiO6 octahedra that share corners with six NiO4 tetrahedra, edges with two equivalent NiO6 octahedra, and edges with four MgO6 octahedra. There are a spread of Ni–O bond distances ranging from 1.87–2.02 Å. In the eighth Ni3+ site, Ni3+ is bonded to four O2- atoms to form NiO4 tetrahedra that share corners with six MgO6 octahedra and corners with six NiO6 octahedra. The corner-sharing octahedra tilt angles range from 54–62°. There is three shorter (1.91 Å) and one longer (1.93 Å) Ni–O bond length. In the ninth Ni3+ site, Ni3+ is bonded to six O2- atoms to form NiO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with five NiO4 tetrahedra, edges with three MgO6 octahedra, and edges with three NiO6 octahedra. There are a spread of Ni–O bond distances ranging from 1.91–2.10 Å. In the tenth Ni3+ site, Ni3+ is bonded to four O2- atoms to form NiO4 tetrahedra that share corners with six MgO6 octahedra and corners with six NiO6 octahedra. The corner-sharing octahedra tilt angles range from 56–63°. There are a spread of Ni–O bond distances ranging from 1.90–2.02 Å. In the eleventh Ni3+ site, Ni3+ is bonded to six O2- atoms to form NiO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent NiO4 tetrahedra, edges with two MgO6 octahedra, and edges with four NiO6 octahedra. There are a spread of Ni–O bond distances ranging from 1.87–1.91 Å. In the twelfth Ni3+ site, Ni3+ is bonded to four O2- atoms to form NiO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine NiO6 octahedra. The corner-sharing octahedra tilt angles range from 49–62°. There is two shorter (1.96 Å) and two longer (1.98 Å) Ni–O bond length. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded to two Mg2+ and two Ni3+ atoms to form distorted OMg2Ni2 trigonal pyramids that share a cornercorner with one OMg2Ni2 tetrahedra, corners with five OMgNi3 trigonal pyramids, and an edgeedge with one OMg2Ni2 trigonal pyramid. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two equivalent Ni3+ atoms. In the third O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Ni3+ atoms. In the fourth O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Ni3+ atoms. In the fifth O2- site, O2- is bonded to two Mg2+ and two Ni3+ atoms to form a mixture of distorted corner and edge-sharing OMg2Ni2 trigonal pyramids. In the sixth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Ni3+ atoms. In the seventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Ni3+ atoms. In the eighth O2- site, O2- is bonded to one Mg2+ and three Ni3+ atoms to form distorted corner-sharing OMgNi3 trigonal pyramids. In the ninth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Ni3+ atoms. In the tenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Ni3+ atoms. In the eleventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Ni3+ atoms. In the twelfth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Ni3+ atoms. In the thirteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Ni3+ atoms. In the fourteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Ni3+ atoms. In the fifteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Ni3+ atoms. In the sixteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Ni3+ atoms. In the seventeenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Ni3+ atoms. In the eighteenth O2- site, O2- is bonded to two Mg2+ and two Ni3+ atoms to form a mixture of distorted corner and edge-sharing OMg2Ni2 trigonal pyramids. In the nineteenth O2- site, O2- is bonded to two Mg2+ and two equivalent Ni3+ atoms to form distorted corner-sharing OMg2Ni2 tetrahedra. In the twentieth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Ni3+ atoms. In the twenty-first O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Ni3+ atoms. In the twenty-second O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Ni3+ atoms. In the twenty-third O2- site, O2- is bonded to one Mg2+ and three Ni3+ atoms to form distorted OMgNi3 trigonal pyramids that share corners with two equivalent OMg2Ni2 tetrahedra, corners with four OMgNi3 trigonal pyramids, and an edgeedge with one OMgNi3 trigonal pyramid. In the twenty-fourth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Ni3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg(MoO2)2 by Materials Project

Mg(MoO2)2 is Spinel-like structured and crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are eight inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine MoO6 octahedra. The corner-sharing octahedra tilt angles range from 52–59°. There are a spread of Mg–O bond distances ranging from 2.02–2.07 Å. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent MoO4 tetrahedra, corners with three MgO4 tetrahedra, a cornercorner with one MoO4 trigonal pyramid, and edges with six MoO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.14–2.16 Å. In the third Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine MoO6 octahedra. The corner-sharing octahedra tilt angles range from 53–60°. There are a spread of Mg–O bond distances ranging from 2.03–2.08 Å. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with three MoO4 tetrahedra, a cornercorner with one MoO4 trigonal pyramid, an edgeedge with one MgO6 octahedra, and edges with five MoO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.11–2.20 Å. In the fifth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share a cornercorner with one MoO4 tetrahedra, corners with two equivalent MoO4 trigonal pyramids, edges with two MgO6 octahedra, and edges with four equivalent MoO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.09–2.21 Å. In the sixth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three equivalent MoO4 tetrahedra, corners with three equivalent MoO4 trigonal pyramids, edges with two MgO6 octahedra, and edges with four MoO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.04–2.20 Å. In the seventh Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with two equivalent MoO4 trigonal pyramids, an edgeedge with one MgO6 octahedra, and edges with five MoO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.04–2.22 Å. In the eighth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share edges with two MgO6 octahedra and edges with four MoO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.08–2.17 Å. There are twelve inequivalent Mo3+ sites. In the first Mo3+ site, Mo3+ is bonded to six O2- atoms to form MoO6 octahedra that share corners with two equivalent MoO4 tetrahedra, corners with three MgO4 tetrahedra, a cornercorner with one MoO4 trigonal pyramid, edges with two equivalent MgO6 octahedra, and edges with four MoO6 octahedra. There are a spread of Mo–O bond distances ranging from 2.15–2.21 Å. In the second Mo3+ site, Mo3+ is bonded to six O2- atoms to form MoO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent MoO4 tetrahedra, edges with two MgO6 octahedra, and edges with four MoO6 octahedra. There are two shorter (2.17 Å) and four longer (2.18 Å) Mo–O bond lengths. In the third Mo3+ site, Mo3+ is bonded to four O2- atoms to form MoO4 trigonal pyramids that share corners with six MgO6 octahedra and corners with six MoO6 octahedra. The corner-sharing octahedra tilt angles range from 42–74°. There are a spread of Mo–O bond distances ranging from 2.02–2.52 Å. In the fourth Mo3+ site, Mo3+ is bonded to six O2- atoms to form MoO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with three MoO4 tetrahedra, a cornercorner with one MoO4 trigonal pyramid, edges with three MgO6 octahedra, and edges with three MoO6 octahedra. There are a spread of Mo–O bond distances ranging from 2.13–2.20 Å. In the fifth Mo3+ site, Mo3+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine MoO6 octahedra. The corner-sharing octahedra tilt angles range from 52–64°. There are a spread of Mo–O bond distances ranging from 2.05–2.22 Å. In the sixth Mo3+ site, Mo3+ is bonded in a distorted trigonal planar geometry to three O2- atoms. There are two shorter (2.00 Å) and one longer (2.01 Å) Mo–O bond lengths. In the seventh Mo3+ site, Mo3+ is bonded to six O2- atoms to form MoO6 octahedra that share a cornercorner with one MoO4 tetrahedra, corners with two equivalent MoO4 trigonal pyramids, edges with two equivalent MoO6 octahedra, and edges with four MgO6 octahedra. There are a spread of Mo–O bond distances ranging from 2.11–2.24 Å. In the eighth Mo3+ site, Mo3+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with six MgO6 octahedra and corners with six MoO6 octahedra. The corner-sharing octahedra tilt angles range from 51–61°. There are a spread of Mo–O bond distances ranging from 1.99–2.04 Å. In the ninth Mo3+ site, Mo3+ is bonded to six O2- atoms to form MoO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with two equivalent MoO4 trigonal pyramids, edges with three MgO6 octahedra, and edges with three MoO6 octahedra. There are a spread of Mo–O bond distances ranging from 2.11–2.21 Å. In the tenth Mo3+ site, Mo3+ is bonded in a trigonal planar geometry to three O2- atoms. All Mo–O bond lengths are 2.01 Å. In the eleventh Mo3+ site, Mo3+ is bonded to six O2- atoms to form MoO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent MoO4 trigonal pyramids, edges with two MgO6 octahedra, and edges with four MoO6 octahedra. There are a spread of Mo–O bond distances ranging from 2.12–2.17 Å. In the twelfth Mo3+ site, Mo3+ is bonded to four O2- atoms to form MoO4 trigonal pyramids that share corners with three MgO6 octahedra and corners with nine MoO6 octahedra. The corner-sharing octahedra tilt angles range from 47–66°. There are a spread of Mo–O bond distances ranging from 1.98–2.35 Å. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Mo3+ atoms. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two equivalent Mo3+ atoms. In the third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Mo3+ atoms. In the fourth O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Mo3+ atoms. In the fifth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Mo3+ atoms. In the sixth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Mo3+ atoms. In the seventh O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Mo3+ atoms. In the eighth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Mo3+ atoms. In the ninth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Mo3+ atoms. In the tenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two Mo3+ atoms. In the eleventh O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Mo3+ atoms. In the twelfth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Mo3+ atoms. In the thirteenth O2- site, O2- is bonded in a 3-coordinate geometry to one Mg2+ and two equivalent Mo3+ atoms. In the fourteenth O2- site, O2- is bonded in a distorted tetrahedral geometry to one Mg2+ and three Mo3+ atoms. In the fifteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Mo3+ atoms. In the sixteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Mo3+ atoms. In the seventeenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Mo3+ atoms. In the eighteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Mo3+ atoms. In the nineteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent Mo3+ atoms. In the twentieth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Mo3+ atoms. In the twenty-first O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Mo3+ atoms. In the twenty-second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Mo3+ atoms. In the twenty-third O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Mo3+ atoms. In the twenty-fourth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to one Mg2+ and two equivalent Mo3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg(WO2)2 by Materials Project

Mg(WO2)2 is beta indium sulfide-derived structured and crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are eight inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine WO6 octahedra. The corner-sharing octahedra tilt angles range from 50–62°. There are a spread of Mg–O bond distances ranging from 2.02–2.06 Å. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent WO4 tetrahedra, corners with three MgO4 tetrahedra, a cornercorner with one WO4 trigonal pyramid, and edges with six WO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.12–2.18 Å. In the third Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine WO6 octahedra. The corner-sharing octahedra tilt angles range from 52–64°. There are a spread of Mg–O bond distances ranging from 2.06–2.13 Å. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share a cornercorner with one WO4 tetrahedra, corners with two equivalent MgO4 tetrahedra, corners with three WO4 trigonal pyramids, an edgeedge with one MgO6 octahedra, and edges with five WO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.12–2.17 Å. In the fifth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three WO4 trigonal pyramids, edges with two MgO6 octahedra, and edges with four equivalent WO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.05–2.16 Å. In the sixth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six WO4 trigonal pyramids, edges with two MgO6 octahedra, and edges with four WO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.05–2.19 Å. In the seventh Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with two equivalent WO4 trigonal pyramids, an edgeedge with one MgO6 octahedra, and edges with five WO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.04–2.24 Å. In the eighth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share edges with two MgO6 octahedra and edges with four WO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.11–2.17 Å. There are twelve inequivalent W3+ sites. In the first W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with two equivalent WO4 tetrahedra, corners with three MgO4 tetrahedra, a cornercorner with one WO4 trigonal pyramid, edges with two equivalent MgO6 octahedra, and edges with four WO6 octahedra. There are a spread of W–O bond distances ranging from 2.16–2.21 Å. In the second W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent WO4 tetrahedra, edges with two MgO6 octahedra, and edges with four WO6 octahedra. There are a spread of W–O bond distances ranging from 2.18–2.22 Å. In the third W3+ site, W3+ is bonded to four O2- atoms to form distorted WO4 trigonal pyramids that share corners with six MgO6 octahedra and corners with six WO6 octahedra. The corner-sharing octahedra tilt angles range from 39–71°. There are a spread of W–O bond distances ranging from 2.03–2.31 Å. In the fourth W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share a cornercorner with one WO4 tetrahedra, corners with two equivalent MgO4 tetrahedra, corners with three WO4 trigonal pyramids, edges with three MgO6 octahedra, and edges with three WO6 octahedra. There are a spread of W–O bond distances ranging from 2.16–2.24 Å. In the fifth W3+ site, W3+ is bonded to four O2- atoms to form WO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine WO6 octahedra. The corner-sharing octahedra tilt angles range from 52–69°. There are a spread of W–O bond distances ranging from 2.09–2.22 Å. In the sixth W3+ site, W3+ is bonded in a trigonal planar geometry to three O2- atoms. There are two shorter (2.01 Å) and one longer (2.04 Å) W–O bond lengths. In the seventh W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with three WO4 trigonal pyramids, edges with two equivalent WO6 octahedra, and edges with four MgO6 octahedra. There are a spread of W–O bond distances ranging from 2.11–2.23 Å. In the eighth W3+ site, W3+ is bonded to four O2- atoms to form WO4 trigonal pyramids that share corners with six MgO6 octahedra and corners with six WO6 octahedra. The corner-sharing octahedra tilt angles range from 37–70°. There are a spread of W–O bond distances ranging from 2.01–2.27 Å. In the ninth W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with two equivalent WO4 trigonal pyramids, edges with three MgO6 octahedra, and edges with three WO6 octahedra. There are a spread of W–O bond distances ranging from 2.13–2.22 Å. In the tenth W3+ site, W3+ is bonded in a trigonal planar geometry to three O2- atoms. There are two shorter (2.02 Å) and one longer (2.03 Å) W–O bond lengths. In the eleventh W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent WO4 trigonal pyramids, edges with two MgO6 octahedra, and edges with four WO6 octahedra. There are a spread of W–O bond distances ranging from 2.06–2.11 Å. In the twelfth W3+ site, W3+ is bonded to four O2- atoms to form WO4 trigonal pyramids that share corners with three MgO6 octahedra and corners with nine WO6 octahedra. The corner-sharing octahedra tilt angles range from 46–70°. There are a spread of W–O bond distances ranging from 2.11–2.29 Å. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two W3+ atoms. In the second O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent W3+ atoms. In the third O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three W3+ atoms. In the fourth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four W3+ atoms. In the fifth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two W3+ atoms. In the sixth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three W3+ atoms. In the seventh O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three W3+ atoms. In the eighth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three W3+ atoms. In the ninth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three W3+ atoms. In the tenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two W3+ atoms. In the eleventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three W3+ atoms. In the twelfth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two W3+ atoms. In the thirteenth O2- site, O2- is bonded in a 3-coordinate geometry to one Mg2+ and two equivalent W3+ atoms. In the fourteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three W3+ atoms. In the fifteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three W3+ atoms. In the sixteenth O2- site, O2- is bonded to one Mg2+ and three W3+ atoms to form distorted corner-sharing OMgW3 tetrahedra. In the seventeenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two W3+ atoms. In the eighteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two W3+ atoms. In the nineteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two equivalent W3+ atoms. In the twentieth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three W3+ atoms. In the twenty-first O2- site, O2- is bonded to one Mg2+ and three W3+ atoms to form distorted corner-sharing OMgW3 tetrahedra. In the twenty-second O2- site, O2- is bonded to four W3+ atoms to form distorted corner-sharing OW4 tetrahedra. In the twenty-third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three W3+ atoms. In the twenty-fourth O2- site, O2- is bonded in a 3-coordinate geometry to one Mg2+ and two equivalent W3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Effects of Zn and Ca on the deformation texture evolution of Mg–Zn–Ca alloys at elevated temperatures

This work utilized crystal plasticity simulations and experimental thermo-mechanical processing to examine how Zn and Ca content affects texture evolution in Mg–Zn–Ca alloys during simulated hot rolling. Four different compositions were studied: unalloyed Mg and three Mg alloys of ZX0p50 (Mg- 0.5 wt% Zn- 0.1 wt% Ca), ZX30 (Mg-3 wt% Zn- 0.1 wt% Ca), and ZX31 (Mg-3 wt% Zn- 0.3 wt% Ca). Multi-pass Gleeble experiments simulated hot rolling using plane strain conditions. Unalloyed Mg developed a strong basal texture, while the addition of Zn and Ca significantly weakened the texture in ZX30 and ZX31; this reduction was not seen in ZX0p50. Notably, ZX31 exhibited a split basal texture aligned with the rolling direction. Crystal plasticity simulations revealed that the weaker basal texture in ZX30 and ZX31 resulted from reduced activation of basal and twinning modes compared to unalloyed Mg and Zx0p50. Increased Zn and Ca content raised the ratios of basal to pyramidal critical resolved sheer stress (CRSS) and twin to pyramidal CRSS, enhancing pyramidal slip activity and weakening the basal texture. Extension twinning played a critical role in texture development during the first deformation pass. In unalloyed Mg and ZX0p50, twinning led to a strong basal texture, while ZX30 and ZX31 had weak basal textures that increased only slightly with further deformation. The split basal poles simulated in ZX31 were consistent with the experimental findings, highlighting the interplay between alloy composition and texture evolution.

Crystal plasticity finite element↗
DOE OSTI2020

Probing Mg Intercalation in the Tetragonal Tungsten Bronze Framework V 4 Nb 18 O 55

While commercial Li-ion batteries offer the highest energy densities of current rechargeable battery technologies, their energy storage limit has almost been achieved. Therefore, there is considerable interest in Mg batteries, which could offer increased energy densities in comparison to Li-ion batteries if a high-voltage electrode material, such as a transition-metal oxide, can be developed. However, there are currently very few oxide materials which have demonstrated reversible and efficient Mg 2+ insertion and extraction at high voltages; this is thought to be due to poor Mg 2+ diffusion kinetics within the oxide structural framework. Here, in this paper, the authors provide conclusive evidence of electrochemical insertion of Mg 2+ into the tetragonal tungsten bronze V 4 Nb 18 O 55 , with a maximum reversible electrochemical capacity of 75 mA h g –1 , which corresponds to a magnesiated composition of Mg 4 V 4 Nb 18 O 55 . Experimental electrochemical magnesiation/demagnesiation revealed a large voltage hysteresis with charge/discharge (1.12 V vs Mg/Mg 2+ ); when magnesiation is limited to a composition of Mg 2 V 4 Nb 18 O 55 , this hysteresis can be reduced to only 0.5 V. Hybrid-exchange density functional theory (DFT) calculations suggest that a limited number of Mg sites are accessible via low-energy diffusion pathways, but that larger kinetic barriers need to be overcome to access the entire structure. The reversible Mg 2+ intercalation involved concurrent V and Nb redox activity and changes in crystal structure, as confirmed by an array of complementary methods, including powder X-ray diffraction, X-ray absorption spectroscopy, and energy-dispersive X-ray spectroscopy. Consequently, it can be concluded that the tetragonal tungsten bronzes show promise as intercalation electrode materials for Mg batteries.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Heteroatom-Doped Graphenes as Actively Interacting 2D Encapsulation Media for Mg-Based Hydrogen Storage

Nanoencapsulation using graphene derivatives enables the facile fabrication of two-dimensional (2D) nanocomposites with unique microstructures and has been generally applied to many fields of energy materials. Particularly, metal hydrides such as MgH 2 encapsulated by graphene derivatives have emerged as a promising hybrid material for overcoming the disadvantageous properties of Mg-based hydrogen storage. Although the behavior of the graphene–Mg nanoencapsulation interface has been studied for many composite materials, the direct modification of graphene with nonmetal foreign elements for changing the interfacial behavior has been limitedly reported. In this regard, using B-doped graphene and N-doped graphene as nanoencapsulation media for tuning the interfacial behavior of graphene derivative–Mg nanoparticles, we present altered hydrogen storage kinetics of heteroatom-doped (B and N) graphene–Mg composites. The effect of heteroatom doping is studied in terms of bonding configurations and heteroatom doping concentrations. The enhancement in hydrogen uptake was observed for all of the heteroatom-doped graphene–Mg nanocomposites. On the other hand, a few samples exhibit significantly low activation energy at the early stage of desorption, which can be related to the facilitated nucleus formation. Density functional theory calculation indicates that B-doping and N-doping accelerate hydrogen absorption kinetics in different ways, aiding charge transfer and inducing surface deformation of Mg nanoparticles, respectively. Their effects can be augmented in the presence of structural defects on graphene, such as vacancies, pores, or graphene edges. These results demonstrate that hydrogen storage kinetics of Mg-based systems can be altered by utilizing heteroatom-doped graphene oxide derivatives as 2D nanoencapsulation media, suggesting that the addition of a nonmetal doping element can also be applied to Mg-based hydrogen storage by modifying the nanoencapsulation interface without forming Mg alloy phases.

08 HYDROGEN↗
DOE OSTI2020

Spectral variability of a sample of extreme variability quasars and implications for the MgII broad-line region

We present new Gemini/GMOS optical spectroscopy of 16 extreme variability quasars (EVQs) that dimmed bymore than 1.5mag in the g band between the Sloan Digital Sky Survey (SDSS) and the Dark Energy Survey epochs (separated by a few years in the quasar rest frame). These EVQs are selected from quasars in the SDSS Stripe 82 region, covering a redshift range of 0.5 < z < 2.1. Nearly half of these EVQs brightened significantly (by more than 0.5 mag in the g band) in a few years after reaching their previous faintest state, and some EVQs showed rapid (non-blazar) variations of greater than 1-2 mag on time-scales of only months. To increase sample statistics, we use a supplemental sample of 33 EVQs with multi-epoch spectra from SDSS that cover the broad Mg II lambda 2798 line. Leveraging on the large dynamic range in continuum variability between the multi-epoch spectra, we explore the associated variations in the broad MgII line, whose variability properties have not been well studied before. The broad MgII flux varies in the same direction as the continuum flux, albeit with a smaller amplitude, which indicates at least some portion of Mg II is reverberating to continuum changes. However, the full width at half-maximum (FWHM) of Mg II does not vary accordingly as continuum changes for most objects in the sample, in contrast to the case of the broad Balmer lines. Using the width of broad MgII to estimate the black hole mass with single epoch spectra therefore introduces a luminosity-dependent bias.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Materials Data on Mg(FeO2)2 by Materials Project

MgFe2O4 is Spinel-like structured and crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are eight inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine FeO6 octahedra. The corner-sharing octahedra tilt angles range from 56–59°. There is two shorter (1.98 Å) and two longer (2.01 Å) Mg–O bond length. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three MgO4 tetrahedra, corners with three FeO4 tetrahedra, and edges with six FeO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.08–2.11 Å. In the third Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine FeO6 octahedra. The corner-sharing octahedra tilt angles range from 56–59°. There are a spread of Mg–O bond distances ranging from 1.99–2.02 Å. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four FeO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five FeO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.08–2.11 Å. In the fifth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six FeO4 tetrahedra, edges with two MgO6 octahedra, and edges with four equivalent FeO6 octahedra. There are two shorter (2.09 Å) and four longer (2.10 Å) Mg–O bond lengths. In the sixth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six FeO4 tetrahedra, edges with two MgO6 octahedra, and edges with four FeO6 octahedra. All Mg–O bond lengths are 2.10 Å. In the seventh Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with five FeO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five FeO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.07–2.11 Å. In the eighth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six FeO4 tetrahedra, edges with two MgO6 octahedra, and edges with four FeO6 octahedra. There are three shorter (2.09 Å) and three longer (2.11 Å) Mg–O bond lengths. There are twelve inequivalent Fe3+ sites. In the first Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with three MgO4 tetrahedra, corners with three FeO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.00–2.11 Å. In the second Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent FeO4 tetrahedra, edges with two MgO6 octahedra, and edges with four FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.00–2.11 Å. In the third Fe3+ site, Fe3+ is bonded to four O2- atoms to form FeO4 tetrahedra that share corners with six MgO6 octahedra and corners with six FeO6 octahedra. The corner-sharing octahedra tilt angles range from 56–57°. There are a spread of Fe–O bond distances ranging from 1.92–1.98 Å. In the fourth Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four FeO4 tetrahedra, edges with three MgO6 octahedra, and edges with three FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.01–2.09 Å. In the fifth Fe3+ site, Fe3+ is bonded to four O2- atoms to form FeO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine FeO6 octahedra. The corner-sharing octahedra tilt angles range from 56–58°. There is three shorter (1.93 Å) and one longer (1.99 Å) Fe–O bond length. In the sixth Fe3+ site, Fe3+ is bonded to four O2- atoms to form FeO4 tetrahedra that share corners with six MgO6 octahedra and corners with six FeO6 octahedra. The corner-sharing octahedra tilt angles range from 56–58°. There are a spread of Fe–O bond distances ranging from 1.91–1.97 Å. In the seventh Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six FeO4 tetrahedra, edges with two equivalent FeO6 octahedra, and edges with four MgO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.04–2.08 Å. In the eighth Fe3+ site, Fe3+ is bonded to four O2- atoms to form FeO4 tetrahedra that share corners with six MgO6 octahedra and corners with six FeO6 octahedra. The corner-sharing octahedral tilt angles are 57°. There are a spread of Fe–O bond distances ranging from 1.91–1.98 Å. In the ninth Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with five FeO4 tetrahedra, edges with three MgO6 octahedra, and edges with three FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.01–2.10 Å. In the tenth Fe3+ site, Fe3+ is bonded to four O2- atoms to form FeO4 tetrahedra that share corners with six MgO6 octahedra and corners with six FeO6 octahedra. The corner-sharing octahedra tilt angles range from 56–58°. There are a spread of Fe–O bond distances ranging from 1.91–1.98 Å. In the eleventh Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent FeO4 tetrahedra, edges with two MgO6 octahedra, and edges with four FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.00–2.10 Å. In the twelfth Fe3+ site, Fe3+ is bonded to four O2- atoms to form FeO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine FeO6 octahedra. The corner-sharing octahedra tilt angles range from 57–58°. There are a spread of Fe–O bond distances ranging from 1.93–1.99 Å. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Fe3+ atoms. In the second O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent Fe3+ atoms. In the third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Fe3+ atoms. In the fourth O2- site, O2- is bonded to four Fe3+ atoms to form a mixture of distorted corner and edge-sharing OFe4 trigonal pyramids. In the fifth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Fe3+ atoms. In the sixth O2- site, O2- is bonded to one Mg2+ and three Fe3+ atoms to form distorted OMgFe3 trigonal pyramids that share corners with two OFe4 trigonal pyramids and edges with three OMgFe3 trigonal pyramids. In the seventh O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Fe3+ atoms. In the eighth O2- site, O2- is bonded to one Mg2+ and three Fe3+ atoms to form a mixture of distorted corner and edge-sharing OMgFe3 trigonal pyramids. In the ninth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Fe3+ atoms. In the tenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two Fe3+ atoms. In the eleventh O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Fe3+ atoms. In the twelfth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two Fe3+ atoms. In the thirteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Fe3+ atoms. In the fourteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Fe3+ atoms. In the fifteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Fe3+ atoms. In the sixteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Fe3+ atoms. In the seventeenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Fe3+ atoms. In the eighteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two Fe3+ atoms. In the nineteenth O2- site, O2- is bonded to two Mg2+ and two equivalent Fe3+ atoms to form distorted corner-sharing OMg2Fe2 trigonal pyramids. In the twentieth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Fe3+ atoms. In the twenty-first O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Fe3+ atoms. In the twenty-second O2- site, O2- is bonded to four Fe3+ atoms to form distorted OFe4 trigonal pyramids that share corners with five OMg2Fe2 trigonal pyramids and edges with three OMgFe3 trigonal pyramids. In the twenty-third O2- site, O2- is bonded to one Mg2+ and three Fe3+ atoms to form distorted OMgFe3 trigonal pyramids that share corners with five OMg2Fe2 trigonal pyramids and edges with three OFe4 trigonal pyramids. In the twenty-fourth O2- site, O2- is bonded to one Mg2+ and three Fe3+ atoms to form distorted OMgFe3 trigonal pyramids that share corners with three equivalent OMg2Fe2 trigonal pyramids and edges with three OFe4 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg(GaO2)2 by Materials Project

MgGa2O4 is Spinel-like structured and crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are eight inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine GaO6 octahedra. The corner-sharing octahedra tilt angles range from 57–59°. There is three shorter (1.97 Å) and one longer (2.00 Å) Mg–O bond length. In the second Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine GaO6 octahedra. The corner-sharing octahedra tilt angles range from 56–60°. There is two shorter (1.96 Å) and two longer (1.99 Å) Mg–O bond length. In the third Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three MgO4 tetrahedra, corners with three GaO4 tetrahedra, and edges with six GaO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.05–2.09 Å. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with five GaO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five GaO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.04–2.09 Å. In the fifth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six GaO4 tetrahedra, edges with two MgO6 octahedra, and edges with four equivalent GaO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.06–2.09 Å. In the sixth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six GaO4 tetrahedra, edges with two MgO6 octahedra, and edges with four GaO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.06–2.11 Å. In the seventh Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four GaO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five GaO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.05–2.09 Å. In the eighth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six GaO4 tetrahedra, edges with two MgO6 octahedra, and edges with four GaO6 octahedra. There are four shorter (2.07 Å) and two longer (2.10 Å) Mg–O bond lengths. There are twelve inequivalent Ga3+ sites. In the first Ga3+ site, Ga3+ is bonded to four O2- atoms to form GaO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine GaO6 octahedra. The corner-sharing octahedra tilt angles range from 56–59°. There are a spread of Ga–O bond distances ranging from 1.89–1.96 Å. In the second Ga3+ site, Ga3+ is bonded to four O2- atoms to form GaO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine GaO6 octahedra. The corner-sharing octahedra tilt angles range from 57–59°. There are a spread of Ga–O bond distances ranging from 1.90–1.96 Å. In the third Ga3+ site, Ga3+ is bonded to four O2- atoms to form GaO4 tetrahedra that share corners with six MgO6 octahedra and corners with six GaO6 octahedra. The corner-sharing octahedra tilt angles range from 55–57°. There is two shorter (1.87 Å) and two longer (1.91 Å) Ga–O bond length. In the fourth Ga3+ site, Ga3+ is bonded to six O2- atoms to form GaO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent GaO4 tetrahedra, edges with two MgO6 octahedra, and edges with four GaO6 octahedra. There are a spread of Ga–O bond distances ranging from 1.96–2.09 Å. In the fifth Ga3+ site, Ga3+ is bonded to six O2- atoms to form GaO6 octahedra that share corners with three MgO4 tetrahedra, corners with three GaO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four GaO6 octahedra. There are a spread of Ga–O bond distances ranging from 1.96–2.09 Å. In the sixth Ga3+ site, Ga3+ is bonded to four O2- atoms to form GaO4 tetrahedra that share corners with six MgO6 octahedra and corners with six GaO6 octahedra. The corner-sharing octahedra tilt angles range from 55–57°. There are a spread of Ga–O bond distances ranging from 1.88–1.93 Å. In the seventh Ga3+ site, Ga3+ is bonded to six O2- atoms to form GaO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent GaO4 tetrahedra, edges with two MgO6 octahedra, and edges with four GaO6 octahedra. There are a spread of Ga–O bond distances ranging from 1.96–2.08 Å. In the eighth Ga3+ site, Ga3+ is bonded to four O2- atoms to form GaO4 tetrahedra that share corners with six MgO6 octahedra and corners with six GaO6 octahedra. The corner-sharing octahedra tilt angles range from 56–58°. There are a spread of Ga–O bond distances ranging from 1.88–1.95 Å. In the ninth Ga3+ site, Ga3+ is bonded to six O2- atoms to form GaO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with five GaO4 tetrahedra, edges with three MgO6 octahedra, and edges with three GaO6 octahedra. There are a spread of Ga–O bond distances ranging from 1.96–2.09 Å. In the tenth Ga3+ site, Ga3+ is bonded to four O2- atoms to form GaO4 tetrahedra that share corners with six MgO6 octahedra and corners with six GaO6 octahedra. The corner-sharing octahedra tilt angles range from 56–57°. There is two shorter (1.88 Å) and two longer (1.93 Å) Ga–O bond length. In the eleventh Ga3+ site, Ga3+ is bonded to six O2- atoms to form GaO6 octahedra that share corners with six GaO4 tetrahedra, edges with two equivalent GaO6 octahedra, and edges with four MgO6 octahedra. There are a spread of Ga–O bond distances ranging from 1.99–2.05 Å. In the twelfth Ga3+ site, Ga3+ is bonded to six O2- atoms to form GaO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four GaO4 tetrahedra, edges with three MgO6 octahedra, and edges with three GaO6 octahedra. There are a spread of Ga–O bond distances ranging from 1.96–2.07 Å. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded to one Mg2+ and three Ga3+ atoms to form a mixture of distorted edge and corner-sharing OMgGa3 trigonal pyramids. In the second O2- site, O2- is bonded to one Mg2+ and three Ga3+ atoms to form a mixture of distorted edge and corner-sharing OMgGa3 trigonal pyramids. In the third O2- site, O2- is bonded to four Ga3+ atoms to form a mixture of distorted edge and corner-sharing OGa4 trigonal pyramids. In the fourth O2- site, O2- is bonded to one Mg2+ and three Ga3+ atoms to form a mixture of distorted edge and corner-sharing OMgGa3 trigonal pyramids. In the fifth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Ga3+ atoms. In the sixth O2- site, O2- is bonded to one Mg2+ and three Ga3+ atoms to form distorted edge-sharing OMgGa3 trigonal pyramids. In the seventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Ga3+ atoms. In the eighth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent Ga3+ atoms. In the ninth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Ga3+ atoms. In the tenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Ga3+ atoms. In the eleventh O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two Ga3+ atoms. In the twelfth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Ga3+ atoms. In the thirteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Ga3+ atoms. In the fourteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two equivalent Ga3+ atoms. In the fifteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Ga3+ atoms. In the sixteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Ga3+ atoms. In the seventeenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Ga3+ atoms. In the eighteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Ga3+ atoms. In the nineteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two Ga3+ atoms. In the twentieth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Ga3+ atoms. In the twenty-first O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Ga3+ atoms. In the twenty-second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Ga3+ atoms. In the twenty-third O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Ga3+ atoms. In the twenty-fourth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Ga3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg(BiO2)2 by Materials Project

Bi2MgO4 is Spinel-like structured and crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are eight inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine BiO6 octahedra. The corner-sharing octahedra tilt angles range from 52–57°. There are two shorter (2.08 Å) and two longer (2.13 Å) Mg–O bond lengths. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three MgO4 tetrahedra, corners with three BiO4 trigonal pyramids, and edges with six BiO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.10–2.40 Å. In the third Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine BiO6 octahedra. The corner-sharing octahedra tilt angles range from 50–58°. There are a spread of Mg–O bond distances ranging from 2.03–2.11 Å. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with three BiO4 tetrahedra, a cornercorner with one BiO4 trigonal pyramid, an edgeedge with one MgO6 octahedra, and edges with five BiO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.08–2.44 Å. In the fifth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six BiO4 tetrahedra, edges with two MgO6 octahedra, and edges with four equivalent BiO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.17–2.26 Å. In the sixth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six BiO4 tetrahedra, edges with two MgO6 octahedra, and edges with four BiO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.11–2.21 Å. In the seventh Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with three BiO4 tetrahedra, corners with two equivalent BiO4 trigonal pyramids, an edgeedge with one MgO6 octahedra, and edges with five BiO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.12–2.54 Å. In the eighth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six BiO4 tetrahedra, edges with two MgO6 octahedra, and edges with four BiO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.16–2.18 Å. There are twelve inequivalent Bi3+ sites. In the first Bi3+ site, Bi3+ is bonded to six O2- atoms to form BiO6 octahedra that share corners with three MgO4 tetrahedra, corners with three BiO4 trigonal pyramids, edges with two equivalent MgO6 octahedra, and edges with four BiO6 octahedra. There are a spread of Bi–O bond distances ranging from 2.39–2.43 Å. In the second Bi3+ site, Bi3+ is bonded to six O2- atoms to form BiO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent BiO4 trigonal pyramids, edges with two MgO6 octahedra, and edges with four BiO6 octahedra. There are a spread of Bi–O bond distances ranging from 2.36–2.47 Å. In the third Bi3+ site, Bi3+ is bonded to four O2- atoms to form BiO4 tetrahedra that share corners with six MgO6 octahedra and corners with six BiO6 octahedra. The corner-sharing octahedra tilt angles range from 50–66°. There are a spread of Bi–O bond distances ranging from 2.21–2.34 Å. In the fourth Bi3+ site, Bi3+ is bonded to six O2- atoms to form BiO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with three BiO4 tetrahedra, a cornercorner with one BiO4 trigonal pyramid, edges with three MgO6 octahedra, and edges with three BiO6 octahedra. There are a spread of Bi–O bond distances ranging from 2.31–2.50 Å. In the fifth Bi3+ site, Bi3+ is bonded to four O2- atoms to form BiO4 trigonal pyramids that share corners with three MgO6 octahedra and corners with nine BiO6 octahedra. The corner-sharing octahedra tilt angles range from 41–68°. There are a spread of Bi–O bond distances ranging from 2.18–2.32 Å. In the sixth Bi3+ site, Bi3+ is bonded to four O2- atoms to form BiO4 tetrahedra that share corners with six MgO6 octahedra and corners with six BiO6 octahedra. The corner-sharing octahedra tilt angles range from 50–67°. There are a spread of Bi–O bond distances ranging from 2.21–2.36 Å. In the seventh Bi3+ site, Bi3+ is bonded to six O2- atoms to form BiO6 octahedra that share corners with six BiO4 tetrahedra, edges with two equivalent BiO6 octahedra, and edges with four MgO6 octahedra. There are a spread of Bi–O bond distances ranging from 2.36–2.41 Å. In the eighth Bi3+ site, Bi3+ is bonded to four O2- atoms to form BiO4 tetrahedra that share corners with six MgO6 octahedra and corners with six BiO6 octahedra. The corner-sharing octahedra tilt angles range from 48–67°. There are a spread of Bi–O bond distances ranging from 2.22–2.33 Å. In the ninth Bi3+ site, Bi3+ is bonded to six O2- atoms to form BiO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with three BiO4 tetrahedra, corners with two equivalent BiO4 trigonal pyramids, edges with three MgO6 octahedra, and edges with three BiO6 octahedra. There are a spread of Bi–O bond distances ranging from 2.29–2.51 Å. In the tenth Bi3+ site, Bi3+ is bonded to four O2- atoms to form BiO4 tetrahedra that share corners with six MgO6 octahedra and corners with six BiO6 octahedra. The corner-sharing octahedra tilt angles range from 49–66°. There are a spread of Bi–O bond distances ranging from 2.21–2.34 Å. In the eleventh Bi3+ site, Bi3+ is bonded to six O2- atoms to form BiO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent BiO4 trigonal pyramids, edges with two MgO6 octahedra, and edges with four BiO6 octahedra. There are a spread of Bi–O bond distances ranging from 2.36–2.57 Å. In the twelfth Bi3+ site, Bi3+ is bonded to four O2- atoms to form BiO4 trigonal pyramids that share corners with three MgO6 octahedra and corners with nine BiO6 octahedra. The corner-sharing octahedra tilt angles range from 38–70°. There are a spread of Bi–O bond distances ranging from 2.15–2.31 Å. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Bi3+ atoms. In the second O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent Bi3+ atoms. In the third O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Bi3+ atoms. In the fourth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Bi3+ atoms. In the fifth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Bi3+ atoms. In the sixth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Bi3+ atoms. In the seventh O2- site, O2- is bonded in a distorted tetrahedral geometry to one Mg2+ and three Bi3+ atoms. In the eighth O2- site, O2- is bonded in a distorted tetrahedral geometry to one Mg2+ and three Bi3+ atoms. In the ninth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Bi3+ atoms. In the tenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two Bi3+ atoms. In the eleventh O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Bi3+ atoms. In the twelfth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two Bi3+ atoms. In the thirteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Bi3+ atoms. In the fourteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Bi3+ atoms. In the fifteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Bi3+ atoms. In the sixteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Bi3+ atoms. In the seventeenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two Bi3+ atoms. In the eighteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two Bi3+ atoms. In the nineteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two equivalent Bi3+ atoms. In the twentieth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Bi3+ atoms. In the twenty-first O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Bi3+ atoms. In the twenty-second O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Bi3+ atoms. In the twenty-third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Bi3+ atoms. In the twenty-fourth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Bi3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg(CuO2)2 by Materials Project

MgCu2O4 is Spinel-like structured and crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are eight inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine CuO6 octahedra. The corner-sharing octahedra tilt angles range from 56–60°. There is three shorter (1.98 Å) and one longer (2.01 Å) Mg–O bond length. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three MgO4 tetrahedra, corners with three CuO4 tetrahedra, and edges with six CuO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.04–2.09 Å. In the third Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine CuO6 octahedra. The corner-sharing octahedra tilt angles range from 57–60°. There are a spread of Mg–O bond distances ranging from 1.98–2.03 Å. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four CuO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five CuO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.04–2.09 Å. In the fifth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six CuO4 tetrahedra, edges with two MgO6 octahedra, and edges with four equivalent CuO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.05–2.08 Å. In the sixth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six CuO4 tetrahedra, edges with two MgO6 octahedra, and edges with four CuO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.05–2.12 Å. In the seventh Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with five CuO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five CuO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.04–2.09 Å. In the eighth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six CuO4 tetrahedra, edges with two MgO6 octahedra, and edges with four CuO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.05–2.10 Å. There are twelve inequivalent Cu3+ sites. In the first Cu3+ site, Cu3+ is bonded to six O2- atoms to form CuO6 octahedra that share corners with three MgO4 tetrahedra, corners with three CuO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four CuO6 octahedra. There are a spread of Cu–O bond distances ranging from 1.95–2.09 Å. In the second Cu3+ site, Cu3+ is bonded to six O2- atoms to form CuO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent CuO4 tetrahedra, edges with two MgO6 octahedra, and edges with four CuO6 octahedra. There are a spread of Cu–O bond distances ranging from 1.95–2.07 Å. In the third Cu3+ site, Cu3+ is bonded to four O2- atoms to form CuO4 tetrahedra that share corners with six MgO6 octahedra and corners with six CuO6 octahedra. The corner-sharing octahedra tilt angles range from 56–59°. All Cu–O bond lengths are 1.93 Å. In the fourth Cu3+ site, Cu3+ is bonded to six O2- atoms to form CuO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four CuO4 tetrahedra, edges with three MgO6 octahedra, and edges with three CuO6 octahedra. There are a spread of Cu–O bond distances ranging from 1.91–2.04 Å. In the fifth Cu3+ site, Cu3+ is bonded to four O2- atoms to form CuO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine CuO6 octahedra. The corner-sharing octahedra tilt angles range from 56–62°. There are a spread of Cu–O bond distances ranging from 1.89–1.98 Å. In the sixth Cu3+ site, Cu3+ is bonded to four O2- atoms to form CuO4 tetrahedra that share corners with six MgO6 octahedra and corners with six CuO6 octahedra. The corner-sharing octahedra tilt angles range from 55–60°. There are a spread of Cu–O bond distances ranging from 1.90–1.92 Å. In the seventh Cu3+ site, Cu3+ is bonded to six O2- atoms to form CuO6 octahedra that share corners with six CuO4 tetrahedra, edges with two equivalent CuO6 octahedra, and edges with four MgO6 octahedra. There are a spread of Cu–O bond distances ranging from 1.92–2.04 Å. In the eighth Cu3+ site, Cu3+ is bonded to four O2- atoms to form CuO4 tetrahedra that share corners with six MgO6 octahedra and corners with six CuO6 octahedra. The corner-sharing octahedra tilt angles range from 55–61°. There is one shorter (1.91 Å) and three longer (1.94 Å) Cu–O bond length. In the ninth Cu3+ site, Cu3+ is bonded to six O2- atoms to form CuO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with five CuO4 tetrahedra, edges with three MgO6 octahedra, and edges with three CuO6 octahedra. There are a spread of Cu–O bond distances ranging from 1.92–2.11 Å. In the tenth Cu3+ site, Cu3+ is bonded to four O2- atoms to form CuO4 tetrahedra that share corners with six MgO6 octahedra and corners with six CuO6 octahedra. The corner-sharing octahedra tilt angles range from 56–59°. There is three shorter (1.92 Å) and one longer (1.99 Å) Cu–O bond length. In the eleventh Cu3+ site, Cu3+ is bonded to six O2- atoms to form CuO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent CuO4 tetrahedra, edges with two MgO6 octahedra, and edges with four CuO6 octahedra. There is four shorter (1.96 Å) and two longer (2.03 Å) Cu–O bond length. In the twelfth Cu3+ site, Cu3+ is bonded to four O2- atoms to form CuO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine CuO6 octahedra. The corner-sharing octahedra tilt angles range from 54–63°. There are a spread of Cu–O bond distances ranging from 1.89–2.00 Å. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded to two Mg2+ and two Cu3+ atoms to form a mixture of distorted corner and edge-sharing OMg2Cu2 trigonal pyramids. In the second O2- site, O2- is bonded to two Mg2+ and two equivalent Cu3+ atoms to form a mixture of distorted corner and edge-sharing OMg2Cu2 trigonal pyramids. In the third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Cu3+ atoms. In the fourth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Cu3+ atoms. In the fifth O2- site, O2- is bonded to two Mg2+ and two Cu3+ atoms to form distorted OMg2Cu2 trigonal pyramids that share corners with three OMg2Cu2 trigonal pyramids and edges with two OMgCu3 trigonal pyramids. In the sixth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Cu3+ atoms. In the seventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cu3+ atoms. In the eighth O2- site, O2- is bonded to one Mg2+ and three Cu3+ atoms to form distorted corner-sharing OMgCu3 trigonal pyramids. In the ninth O2- site, O2- is bonded to one Mg2+ and three Cu3+ atoms to form a mixture of distorted corner and edge-sharing OMgCu3 trigonal pyramids. In the tenth O2- site, O2- is bonded to two Mg2+ and two Cu3+ atoms to form a mixture of distorted corner and edge-sharing OMg2Cu2 trigonal pyramids. In the eleventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cu3+ atoms. In the twelfth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Cu3+ atoms. In the thirteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cu3+ atoms. In the fourteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cu3+ atoms. In the fifteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cu3+ atoms. In the sixteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cu3+ atoms. In the seventeenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Cu3+ atoms. In the eighteenth O2- site, O2- is bonded to two Mg2+ and two Cu3+ atoms to form a mixture of distorted corner and edge-sharing OMg2Cu2 trigonal pyramids. In the nineteenth O2- site, O2- is bonded to two Mg2+ and two equivalent Cu3+ atoms to form distorted corner-sharing OMg2Cu2 trigonal pyramids. In the twentieth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cu3+ atoms. In the twenty-first O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cu3+ atoms. In the twenty-second O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Cu3+ atoms. In the twenty-third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Cu3+ atoms. In the twenty-fourth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cu3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg(SbO2)2 by Materials Project

MgSb2O4 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are eight inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Mg–O bond distances ranging from 2.11–2.49 Å. In the second Mg2+ site, Mg2+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Mg–O bond distances ranging from 2.05–2.30 Å. In the third Mg2+ site, Mg2+ is bonded to four O2- atoms to form corner-sharing MgO4 trigonal pyramids. The corner-sharing octahedral tilt angles are 42°. There are a spread of Mg–O bond distances ranging from 1.97–2.21 Å. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form distorted MgO6 octahedra that share a cornercorner with one SbO4 tetrahedra, corners with two equivalent MgO4 trigonal pyramids, and an edgeedge with one MgO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.06–2.57 Å. In the fifth Mg2+ site, Mg2+ is bonded to five O2- atoms to form MgO5 square pyramids that share corners with two equivalent SbO6 octahedra, corners with two equivalent SbO4 tetrahedra, edges with two MgO6 octahedra, and edges with two equivalent SbO6 octahedra. The corner-sharing octahedral tilt angles are 70°. There are a spread of Mg–O bond distances ranging from 2.07–2.22 Å. In the sixth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three equivalent SbO4 tetrahedra, an edgeedge with one MgO6 octahedra, edges with two equivalent SbO6 octahedra, and an edgeedge with one MgO5 square pyramid. There are a spread of Mg–O bond distances ranging from 2.01–2.22 Å. In the seventh Mg2+ site, Mg2+ is bonded to five O2- atoms to form distorted MgO5 trigonal bipyramids that share corners with two equivalent SbO4 trigonal pyramids, an edgeedge with one MgO6 octahedra, and an edgeedge with one SbO5 square pyramid. There are a spread of Mg–O bond distances ranging from 2.01–2.19 Å. In the eighth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share edges with two equivalent SbO6 octahedra, an edgeedge with one MgO5 square pyramid, and an edgeedge with one MgO5 trigonal bipyramid. There are a spread of Mg–O bond distances ranging from 2.00–2.37 Å. There are twelve inequivalent Sb3+ sites. In the first Sb3+ site, Sb3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Sb–O bond distances ranging from 2.02–2.82 Å. In the second Sb3+ site, Sb3+ is bonded in a distorted T-shaped geometry to three O2- atoms. There are two shorter (1.96 Å) and one longer (2.06 Å) Sb–O bond lengths. In the third Sb3+ site, Sb3+ is bonded to four O2- atoms to form distorted SbO4 tetrahedra that share corners with four MgO6 octahedra, corners with four equivalent SbO6 octahedra, and corners with two equivalent MgO5 square pyramids. The corner-sharing octahedra tilt angles range from 18–66°. There are a spread of Sb–O bond distances ranging from 1.97–2.64 Å. In the fourth Sb3+ site, Sb3+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Sb–O bond distances ranging from 2.07–2.81 Å. In the fifth Sb3+ site, Sb3+ is bonded in a distorted T-shaped geometry to three O2- atoms. There are two shorter (1.98 Å) and one longer (2.02 Å) Sb–O bond lengths. In the sixth Sb3+ site, Sb3+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of Sb–O bond distances ranging from 1.98–2.66 Å. In the seventh Sb3+ site, Sb3+ is bonded to six O2- atoms to form distorted SbO6 octahedra that share a cornercorner with one MgO5 square pyramid, corners with two equivalent SbO4 tetrahedra, edges with two MgO6 octahedra, edges with two equivalent SbO6 octahedra, and an edgeedge with one MgO5 square pyramid. There are a spread of Sb–O bond distances ranging from 2.05–2.65 Å. In the eighth Sb3+ site, Sb3+ is bonded in a 3-coordinate geometry to three O2- atoms. There are two shorter (2.03 Å) and one longer (2.08 Å) Sb–O bond lengths. In the ninth Sb3+ site, Sb3+ is bonded in a distorted see-saw-like geometry to four O2- atoms. There are a spread of Sb–O bond distances ranging from 2.08–2.34 Å. In the tenth Sb3+ site, Sb3+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of Sb–O bond distances ranging from 1.96–2.81 Å. In the eleventh Sb3+ site, Sb3+ is bonded to five O2- atoms to form distorted SbO5 square pyramids that share corners with two equivalent SbO4 trigonal pyramids and an edgeedge with one MgO5 trigonal bipyramid. There are a spread of Sb–O bond distances ranging from 2.02–2.56 Å. In the twelfth Sb3+ site, Sb3+ is bonded to four O2- atoms to form SbO4 trigonal pyramids that share corners with two equivalent SbO5 square pyramids and corners with two equivalent MgO5 trigonal bipyramids. There are two shorter (2.01 Å) and two longer (2.15 Å) Sb–O bond lengths. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to two Mg2+ and two Sb3+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mg2+ and two equivalent Sb3+ atoms. In the third O2- site, O2- is bonded in a trigonal non-coplanar geometry to three Sb3+ atoms. In the fourth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to four Sb3+ atoms. In the fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Mg2+ and one Sb3+ atom. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to two Mg2+ and two Sb3+ atoms. In the seventh O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Mg2+ and three Sb3+ atoms. In the eighth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Mg2+ and three Sb3+ atoms. In the ninth O2- site, O2- is bonded in a 3-coordinate geometry to one Mg2+ and two equivalent Sb3+ atoms. In the tenth O2- site, O2- is bonded to two Mg2+ and two Sb3+ atoms to form a mixture of distorted edge and corner-sharing OMg2Sb2 tetrahedra. In the eleventh O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to one Mg2+ and two equivalent Sb3+ atoms. In the twelfth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two Sb3+ atoms. In the thirteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Sb3+ atoms. In the fourteenth O2- site, O2- is bonded in a trigonal non-coplanar geometry to one Mg2+ and two equivalent Sb3+ atoms. In the fifteenth O2- site, O2- is bonded in a 4-coordinate geometry to one Mg2+ and three Sb3+ atoms. In the sixteenth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to one Mg2+ and three Sb3+ atoms. In the seventeenth O2- site, O2- is bonded to two Mg2+ and two Sb3+ atoms to form a mixture of distorted edge and corner-sharing OMg2Sb2 tetrahedra. In the eighteenth O2- site, O2- is bonded in a 4-coordinate geometry to two Mg2+ and two Sb3+ atoms. In the nineteenth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mg2+ and two equivalent Sb3+ atoms. In the twentieth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Sb3+ atoms. In the twenty-first O2- site, O2- is bonded in a trigonal non-coplanar geometry to one Mg2+ and two equivalent Sb3+ atoms. In the twenty-second O2- site, O2- is bonded in a 4-coordinate geometry to four Sb3+ atoms. In the twenty-third O2- site, O2- is bonded in a 3-coordinate geometry to one Mg2+ and two Sb3+ atoms. In the twenty-fourth O2- site, O2- is bonded in a bent 120 degrees geometry to one Mg2+ and one Sb3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Coordination-Dependent Chemical Reactivity of TFSI Anions at a Mg Metal Interface

Charge transfer across the electrode–electrolyte interface is a highly complex and convoluted process involving diverse solvated species with varying structures and compositions. Despite recent advances in in situ and operando interfacial analysis, molecular specific reactivity of solvated species is inaccessible due to a lack of precise control over the interfacial constituents and/or an unclear understanding of their spectroscopic fingerprints. However, such molecular-specific understanding is critical to the rational design of energy-efficient solid–electrolyte interphase layers. We have employed ion soft landing, a versatile and highly controlled method, to prepare well-defined interfaces assembled with selected ions, either as solvated species or as bare ions, with distinguishing molecular precision. Equipped with precise control over interfacial composition, we employed in situ multimodal spectroscopic characterization to unravel the molecular specific reactivity of Mg solvated species comprising (i.e., bis(trifluoromethanesulfonyl)imide, TFSI – ) anions and solvent molecules (i.e., dimethoxyethane, DME/G1) on a Mg metal surface relevant to multivalent Mg batteries. In situ multimodal spectroscopic characterization revealed higher reactivity of the undercoordinated solvated species [Mg-TFSI-G1] + compared to the fully coordinated [Mg-TFSI-(G1) 2 ] + species or even the bare TFSI – . These results were corroborated by the computed reaction pathways and energy barriers for decomposition of the TFSI – within Mg solvated species relative to bare TFSI – . Finally, we evaluated the TFSI reactivity under electrochemical conditions using Mg(TFSI) 2 –DME-based phase-separated electrolytes representing different solvated constituents. Based on our multimodal study, we report a detailed understanding of TFSI – decomposition processes as part of coordinated solvated species at a Mg-metal anode that will aid the rational design of improved sustainable electrochemical energy technologies.

25 ENERGY STORAGE↗
DOE OSTI2020

Highly deformable Mg–Al–Ca alloy with Al 2 Ca precipitates

Magnesium (Mg) is the lightest structural metal. However, the poor formability of Mg alloys to great extent limits their applications in making structural parts. Formability is strongly correlated to both high tensile elongation and large work hardening capacity. In this work, we report a new Mg-Al-Ca alloy in which a majority of deformable Al 2 Ca precipitates form while the formation of Laves phases of Mg 17 Al 12 and Mg 2 Ca seems suppressed. Al 2 Ca precipitates imped dislocation motion, leading to large work hardening. Then, Al 2 Ca precipitates deform with dislocations and stacking faults under the enhanced flow stress, which relieve local stress concentration and improve tensile elongation. In addition, solutes Al and Ca suppress twin nucleation while promoting non-basal dislocations in Mg. Our Mg-Al-Ca alloy demonstrates one of the highest combinations of tensile elongation and work hardening capacity among existing Mg alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2023

The combined effects of Mg 2+ and Sr 2+ incorporation during CaCO 3 precipitation and crystal growth

Calcite (CaCO 3 ) composition and properties are defined by the chemical environment in which CaCO 3 forms. However, a complete understanding of the relationship between aqueous chemistry during calcite precipitation and resulting chemical and physical CaCO 3 properties remains elusive; therefore, we present an investigation into the coupled effects of divalent cations Sr 2+ and Mg 2+ on CaCO 3 precipitation and subsequent crystal growth. Through chemical analysis of the aqueous phases and microscopy of the resulting calcite phases in compliment with density functional theory calculations, we elucidate the relationship between crystal growth and the resulting composition (elemental and isotopic) of calcite. The results of this experimental and modeling work suggest that Mg 2+ and Sr 2+ have cation-specific impacts that inhibit calcite crystal growth, including: (1) Sr 2+ incorporates more readily into calcite than Mg 2+ (D Sr > D Mg ), and increasing [Sr 2+ ] t or [Mg 2+ ] t increases D Sr ; (2) the inclusion of Mg 2+ into structure leads to a reduction in the calcite unit cell volume, whereas Sr 2+ leads to an expansion; (3) the inclusion of both Mg 2+ and Sr 2+ results in a distribution of unit cell impacts based on the relative positions of the Sr 2+ and Mg 2+ in the lattice. These experiments were conducted at saturation indices of CaCO 3 of ~4.1, favoring rapid precipitation. This rapid precipitation resulted in observed Sr isotope fractionation confirming Sr isotopic fractionation is dependent upon the precipitation rate. We further note that the precipitation and growth of calcite favors the incorporation of the lighter 86 Sr isotope over the heavier 87 Sr isotope, regardless of the initial solution conditions, and the degree of fractionation increases with D Sr . In sum, these results demonstrate the impact of solution environment to influence the incorporation behavior and crystal growth behavior of calcite. These factors are important to understand in order to effectively use geochemical signatures resulting from calcite precipitation or dissolution to gain specific information.

58 GEOSCIENCES↗
DOE OSTI2022

Facile Electrochemical Mg-Ion Transport in a Defect-Free Spinel Oxide

Inversion, i.e. Mg/Mn antisite disorder, in a spinel oxide simultaneously causes blockage of favorable Mg 2+ migration paths, raising activation barriers for diffusion, and it reduces the number of redox-active metals, limiting the maximum capacity in the spinel. Here, an inversion-free spinel, MgCr 1.5 Mn 0.5 O 4 , was synthesized by exploiting the different intrinsic crystal field stabilization of redox-active Cr and Mn in the form of a solid-solution. The capability of the tailored spinel to reversibly (de)intercalate Mg 2+ at high redox potentials was investigated. The decrease in inversion dramatically lowered the electrochemical overpotential and hysteresis, and enabled utilization of high potentials at ~2.9 V (vs. Mg/Mg 2+ ) upon re-intercalation of Mg 2+ . A combination of characterization techniques reveals that the structural, compositional, and redox changes within the spinel oxide were consistent with the observed electrochemical Mg 2+ activity. Quantification of selective solely to lattice Mg 2+ upon the electrochemical reaction was investigated by monitoring NMR signals in isotope 25 Mg-enriched spinel oxides. Our findings enhance the understanding of Mg 2+ transport within spinel oxide frameworks and provide conclusive evidence for bulk Mg migration in oxide lattices at high redox potentials with minimized electrochemical hysteresis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Carbonation and Sulfidation of Mg- and Ni-Containing Solutions: Implications for Carbon Mineralization and Critical Element Recovery

Carbonation of alkaline earth metals ( e.g. , magnesium (Mg)) and sulfidation of nickel (Ni) are promising methods to achieve concurrent carbon mineralization and selective Ni recovery. However, the coexistence of alkaline earth metals and Ni from silicate ores or mining wastewater complicates the carbonation and sulfidation owing to cation coprecipitation. To better understand simultaneous metal carbonation and Ni-sulfide formation, we used Mg- and Ni-containing solutions and systematically investigated the Mg and Ni coprecipitates’ phase transformation during sequential/concurrent carbonation and sulfidation. During a single carbonation process, hydromagnesite dehydrated and formed magnesite over time. Nickel bicarbonate formed and became a Mg–Ni carbonate solid solution because of their similar ionic radii. During a single sulfidation process, the pH did not affect Ni-sulfide formation, but it controlled Mg behavior. Specifically, at pH 9.6, brucite formed, while at pH 7.8, Mg 2+ remained in the solution. For the sequential carbonation–sulfidation process, Ni-carbonate formed during carbonation converted to Ni-sulfide because of the low Ni-sulfide K sp . For the sulfidation–carbonation process, Ni-sulfide remained the same even after carbonation and Mg-carbonate precipitates. For the concurrent carbonation and sulfidation process, Mg-carbonate and Ni-sulfide formed simultaneously. Finally, this study develops a scientific foundation of carbonation and sulfidation processes, benefiting coupled CO 2 storage and sulfide-enabled resource recovery.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Mg(BH 4 ) 2 -Based Hybrid Metal–Organic Borohydride System Exhibiting Enhanced Chemical Stability in Melt

The formation of a chemically stable and thermally cyclable Mg(BH 4 ) 2 melt is proven to be possible through the utilization of an organic borohydride salt additive. While extensive exploration of additives for lowering the melting point and modifying the chemical stability of Mg(BH 4 ) 2 has been reported, this is the first study to use the organic borohydride salt, tetramethylammonium borohydride (TMAB), to modify the melting behavior of Mg(BH 4 ) 2 . Here, examination of a 5:1 molar mixture of Mg(BH 4 ) 2 and TMAB revealed a reversible melt between 180 and 195 °C, which was reproduced for five thermal cycles. The mixture melt exhibited an enhanced chemical stability compared to melts of the individual Mg(BH 4 ) 2 and TMAB species. It was observed that between room temperature and 250 °C (over 50 °C above the melting point), the mixture releases <0.1 wt % mass, consisting primarily of H 2 . The mixture also exhibits greatly reduced evolution of volatile boron containing compounds compared to either Mg(BH 4 ) 2 or TMAB. The use of TMAB to chemically stabilize a Mg(BH 4 ) 2 -rich melt demonstrated in this work represents an exciting pathway to modification of Mg(BH 4 ) 2 relevant to both hydrogen-storage and magnesium battery fields.

08 HYDROGEN↗