Materials Data on CaCr(Si2O5)2 by Materials Project
CaCr(Si2O5)2 crystallizes in the tetragonal P4/ncc space group. The structure is three-dimensional. Ca2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are four shorter (2.38 Å) and four longer (2.75 Å) Ca–O bond lengths. Cr2+ is bonded in a rectangular see-saw-like geometry to four equivalent O2- atoms. All Cr–O bond lengths are 2.04 Å. Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.61–1.65 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Ca2+ and two equivalent Si4+ atoms. In the second O2- site, O2- is bonded in a linear geometry to two equivalent Si4+ atoms. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ca2+, one Cr2+, and one Si4+ atom.