Materials Data on Ca8Mo7O20 by Materials Project
Ca8Mo7O20 crystallizes in the tetragonal I4/m space group. The structure is three-dimensional. Ca2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ca–O bond distances ranging from 2.22–2.76 Å. There are three inequivalent Mo+3.43+ sites. In the first Mo+3.43+ site, Mo+3.43+ is bonded to five O2- atoms to form MoO5 square pyramids that share a cornercorner with one MoO6 octahedra and corners with four MoO5 square pyramids. The corner-sharing octahedral tilt angles are 24°. There are a spread of Mo–O bond distances ranging from 1.97–2.13 Å. In the second Mo+3.43+ site, Mo+3.43+ is bonded to five O2- atoms to form MoO5 square pyramids that share a cornercorner with one MoO6 octahedra and corners with four equivalent MoO5 square pyramids. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.04 Å) and one longer (2.07 Å) Mo–O bond lengths. In the third Mo+3.43+ site, Mo+3.43+ is bonded to six O2- atoms to form corner-sharing MoO6 octahedra. There are two shorter (2.10 Å) and four longer (2.16 Å) Mo–O bond lengths. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted see-saw-like geometry to two equivalent Ca2+ and two Mo+3.43+ atoms. In the second O2- site, O2- is bonded to four equivalent Ca2+ atoms to form OCa4 tetrahedra that share corners with four equivalent OCa4Mo2 octahedra and corners with four equivalent OCa2Mo2 trigonal pyramids. The corner-sharing octahedral tilt angles are 48°. In the third O2- site, O2- is bonded in a 6-coordinate geometry to four equivalent Ca2+ and two Mo+3.43+ atoms. In the fourth O2- site, O2- is bonded to four equivalent Ca2+ and two Mo+3.43+ atoms to form OCa4Mo2 octahedra that share a cornercorner with one OCa4Mo2 octahedra, corners with four equivalent OCa4 tetrahedra, and corners with four equivalent OCa2Mo2 trigonal pyramids. The corner-sharing octahedral tilt angles are 0°. In the fifth O2- site, O2- is bonded to two equivalent Ca2+ and two equivalent Mo+3.43+ atoms to form OCa2Mo2 trigonal pyramids that share corners with two equivalent OCa4Mo2 octahedra, corners with two equivalent OCa4 tetrahedra, and corners with two equivalent OCa2Mo2 trigonal pyramids. The corner-sharing octahedral tilt angles are 49°.