DOE OSTI2020
CaBi2O4 is Spinel-like structured and crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are six inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to four O2- atoms to form CaO4 tetrahedra that share corners with three CaO6 octahedra and corners with nine BiO6 octahedra. The corner-sharing octahedra tilt angles range from 56–59°. There are two shorter (2.31 Å) and two longer (2.32 Å) Ca–O bond lengths. In the second Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with six BiO4 tetrahedra, edges with two CaO6 octahedra, and edges with four BiO6 octahedra. There are three shorter (2.39 Å) and three longer (2.40 Å) Ca–O bond lengths. In the third Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with two equivalent CaO4 tetrahedra, corners with four BiO4 tetrahedra, an edgeedge with one CaO6 octahedra, and edges with five BiO6 octahedra. There are two shorter (2.39 Å) and four longer (2.40 Å) Ca–O bond lengths. In the fourth Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with six BiO4 tetrahedra, edges with two CaO6 octahedra, and edges with four BiO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.38–2.41 Å. In the fifth Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with six BiO4 tetrahedra, edges with two CaO6 octahedra, and edges with four equivalent BiO6 octahedra. All Ca–O bond lengths are 2.40 Å. In the sixth Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share a cornercorner with one CaO4 tetrahedra, corners with five BiO4 tetrahedra, an edgeedge with one CaO6 octahedra, and edges with five BiO6 octahedra. There are three shorter (2.39 Å) and three longer (2.40 Å) Ca–O bond lengths. There are nine inequivalent Bi3+ sites. In the first Bi3+ site, Bi3+ is bonded to six O2- atoms to form BiO6 octahedra that share corners with two equivalent CaO4 tetrahedra, corners with four BiO4 tetrahedra, edges with three CaO6 octahedra, and edges with three BiO6 octahedra. There are a spread of Bi–O bond distances ranging from 2.37–2.42 Å. In the second Bi3+ site, Bi3+ is bonded to four O2- atoms to form BiO4 tetrahedra that share corners with six CaO6 octahedra and corners with six BiO6 octahedra. The corner-sharing octahedra tilt angles range from 56–59°. There are a spread of Bi–O bond distances ranging from 2.27–2.30 Å. In the third Bi3+ site, Bi3+ is bonded to six O2- atoms to form BiO6 octahedra that share corners with three equivalent CaO4 tetrahedra, corners with three equivalent BiO4 tetrahedra, edges with two CaO6 octahedra, and edges with four BiO6 octahedra. There are a spread of Bi–O bond distances ranging from 2.32–2.50 Å. In the fourth 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 CaO6 octahedra. There are a spread of Bi–O bond distances ranging from 2.39–2.42 Å. In the fifth Bi3+ site, Bi3+ is bonded to four O2- atoms to form BiO4 tetrahedra that share corners with six CaO6 octahedra and corners with six BiO6 octahedra. The corner-sharing octahedra tilt angles range from 56–58°. There are a spread of Bi–O bond distances ranging from 2.27–2.32 Å. In the sixth Bi3+ site, Bi3+ is bonded to six O2- atoms to form BiO6 octahedra that share a cornercorner with one CaO4 tetrahedra, corners with five BiO4 tetrahedra, edges with three CaO6 octahedra, and edges with three BiO6 octahedra. There are a spread of Bi–O bond distances ranging from 2.35–2.46 Å. In the seventh Bi3+ site, Bi3+ is bonded to four O2- atoms to form BiO4 tetrahedra that share corners with six CaO6 octahedra and corners with six BiO6 octahedra. The corner-sharing octahedra tilt angles range from 56–58°. There are a spread of Bi–O bond distances ranging from 2.26–2.30 Å. In the eighth Bi3+ site, Bi3+ is bonded to four O2- atoms to form BiO4 tetrahedra that share corners with six CaO6 octahedra and corners with six BiO6 octahedra. The corner-sharing octahedra tilt angles range from 55–58°. There are a spread of Bi–O bond distances ranging from 2.27–2.30 Å. In the ninth Bi3+ site, Bi3+ is bonded to four O2- atoms to form BiO4 tetrahedra that share corners with three CaO6 octahedra and corners with nine BiO6 octahedra. The corner-sharing octahedra tilt angles range from 55–60°. There are a spread of Bi–O bond distances ranging from 2.25–2.30 Å. There are eighteen inequivalent O2- sites. In the first O2- site, O2- is bonded to two Ca2+ and two Bi3+ atoms to form a mixture of distorted edge and corner-sharing OCa2Bi2 trigonal pyramids. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Ca2+ and three Bi3+ atoms. In the third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Ca2+ and three Bi3+ atoms. In the fourth O2- site, O2- is bonded to two Ca2+ and two Bi3+ atoms to form a mixture of distorted edge and corner-sharing OCa2Bi2 trigonal pyramids. In the fifth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Ca2+ and three Bi3+ atoms. In the sixth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Ca2+ and three Bi3+ atoms. In the seventh O2- site, O2- is bonded to two Ca2+ and two Bi3+ atoms to form a mixture of distorted edge and corner-sharing OCa2Bi2 trigonal pyramids. In the eighth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Ca2+ and three Bi3+ atoms. In the ninth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Ca2+ and three Bi3+ atoms. In the tenth O2- site, O2- is bonded to two Ca2+ and two Bi3+ atoms to form a mixture of distorted edge and corner-sharing OCa2Bi2 trigonal pyramids. In the eleventh O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Ca2+ and three Bi3+ atoms. In the twelfth O2- site, O2- is bonded to two Ca2+ and two Bi3+ atoms to form a mixture of distorted edge and corner-sharing OCa2Bi2 trigonal pyramids. In the thirteenth O2- site, O2- is bonded to two Ca2+ and two equivalent Bi3+ atoms to form a mixture of distorted edge and corner-sharing OCa2Bi2 trigonal pyramids. In the fourteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Ca2+ and three Bi3+ atoms. In the fifteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Ca2+ and three Bi3+ atoms. In the sixteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Bi3+ atoms. In the seventeenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three Bi3+ atoms. In the eighteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three Bi3+ atoms.