DOE OSTI2020
CaV4O8 crystallizes in the triclinic P1 space group. The structure is three-dimensional. Ca2+ is bonded in a 5-coordinate geometry to five O2- atoms. There are four shorter (2.31 Å) and one longer (2.45 Å) Ca–O bond lengths. There are four inequivalent V+3.50+ sites. In the first V+3.50+ site, V+3.50+ is bonded to six O2- atoms to form a mixture of corner and edge-sharing VO6 octahedra. The corner-sharing octahedra tilt angles range from 49–52°. There are a spread of V–O bond distances ranging from 1.82–2.06 Å. In the second V+3.50+ site, V+3.50+ is bonded to six O2- atoms to form a mixture of distorted corner and edge-sharing VO6 octahedra. The corner-sharing octahedra tilt angles range from 49–55°. There are a spread of V–O bond distances ranging from 1.82–2.17 Å. In the third V+3.50+ site, V+3.50+ is bonded to six O2- atoms to form a mixture of corner and edge-sharing VO6 octahedra. The corner-sharing octahedra tilt angles range from 51–52°. There are a spread of V–O bond distances ranging from 1.90–2.08 Å. In the fourth V+3.50+ site, V+3.50+ is bonded to six O2- atoms to form a mixture of corner and edge-sharing VO6 octahedra. The corner-sharing octahedra tilt angles range from 52–55°. There are a spread of V–O bond distances ranging from 1.96–2.20 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a trigonal planar geometry to three V+3.50+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to three V+3.50+ atoms. In the third O2- site, O2- is bonded in a trigonal planar geometry to three V+3.50+ atoms. In the fourth O2- site, O2- is bonded to one Ca2+ and three V+3.50+ atoms to form distorted OCaV3 trigonal pyramids that share corners with two equivalent OCaV3 trigonal pyramids, edges with two equivalent OCa2V3 square pyramids, and edges with two equivalent OCa2V3 trigonal bipyramids. In the fifth O2- site, O2- is bonded in a trigonal non-coplanar geometry to three V+3.50+ atoms. In the sixth O2- site, O2- is bonded to two equivalent Ca2+ and three V+3.50+ atoms to form distorted OCa2V3 trigonal bipyramids that share corners with two equivalent OCa2V3 square pyramids, an edgeedge with one OCa2V3 square pyramid, edges with two equivalent OCa2V3 trigonal bipyramids, and edges with two equivalent OCaV3 trigonal pyramids. In the seventh O2- site, O2- is bonded to two equivalent Ca2+ and three V+3.50+ atoms to form OCa2V3 square pyramids that share corners with two equivalent OCa2V3 trigonal bipyramids, edges with two equivalent OCa2V3 square pyramids, an edgeedge with one OCa2V3 trigonal bipyramid, and edges with two equivalent OCaV3 trigonal pyramids. In the eighth O2- site, O2- is bonded in a trigonal non-coplanar geometry to three V+3.50+ atoms.