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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on CaCr4O8 by Materials Project

CaCr4O8 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Ca2+ is bonded in a 6-coordinate geometry to six equivalent O2- atoms. All Ca–O bond lengths are 2.41 Å. There are two inequivalent Cr+3.50+ sites. In the first Cr+3.50+ site, Cr+3.50+ is bonded to six O2- atoms to form edge-sharing CrO6 octahedra. There is two shorter (1.95 Å) and four longer (1.98 Å) Cr–O bond length. In the second Cr+3.50+ site, Cr+3.50+ is bonded to six equivalent O2- atoms to form edge-sharing CrO6 octahedra. All Cr–O bond lengths are 2.04 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Ca2+ and three Cr+3.50+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three equivalent Cr+3.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CaCr4O8 by Materials Project

CaCr4O8 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. Ca2+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Ca–O bond distances ranging from 2.36–2.62 Å. There are four inequivalent Cr+3.50+ sites. In the first Cr+3.50+ site, Cr+3.50+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing CrO6 octahedra. The corner-sharing octahedra tilt angles range from 51–57°. There are a spread of Cr–O bond distances ranging from 1.97–2.08 Å. In the second Cr+3.50+ site, Cr+3.50+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing CrO6 octahedra. The corner-sharing octahedra tilt angles range from 51–56°. There are a spread of Cr–O bond distances ranging from 1.85–2.11 Å. In the third Cr+3.50+ site, Cr+3.50+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing CrO6 octahedra. The corner-sharing octahedra tilt angles range from 52–57°. There are a spread of Cr–O bond distances ranging from 1.84–2.00 Å. In the fourth Cr+3.50+ site, Cr+3.50+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing CrO6 octahedra. The corner-sharing octahedra tilt angles range from 52–56°. There are a spread of Cr–O bond distances ranging from 1.95–2.08 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a trigonal planar geometry to three Cr+3.50+ atoms. In the second O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+ and three Cr+3.50+ atoms. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to three Cr+3.50+ atoms. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Cr+3.50+ atoms. In the fifth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three Cr+3.50+ atoms. In the sixth O2- site, O2- is bonded to two equivalent Ca2+ and three Cr+3.50+ atoms to form a mixture of distorted edge and corner-sharing OCa2Cr3 trigonal bipyramids. In the seventh O2- site, O2- is bonded to two equivalent Ca2+ and three Cr+3.50+ atoms to form a mixture of distorted edge and corner-sharing OCa2Cr3 trigonal bipyramids. In the eighth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three Cr+3.50+ atoms.

36 MATERIALS SCIENCE↗