DOE OSTI2020
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.