DOE OSTI2020
Ca(CuO2)2 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are two inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ca–O bond distances ranging from 2.26–2.83 Å. In the second Ca2+ site, Ca2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ca–O bond distances ranging from 2.25–2.83 Å. There are four inequivalent Cu3+ sites. In the first Cu3+ site, Cu3+ is bonded to five O2- atoms to form CuO5 square pyramids that share corners with four CuO6 octahedra and edges with two equivalent CuO5 square pyramids. The corner-sharing octahedra tilt angles range from 52–55°. There are a spread of Cu–O bond distances ranging from 1.91–2.06 Å. In the second Cu3+ site, Cu3+ is bonded to six O2- atoms to form CuO6 octahedra that share corners with four CuO5 square pyramids and edges with four CuO6 octahedra. There are a spread of Cu–O bond distances ranging from 1.95–2.05 Å. In the third Cu3+ site, Cu3+ is bonded to six O2- atoms to form CuO6 octahedra that share corners with four CuO5 square pyramids and edges with four CuO6 octahedra. There are a spread of Cu–O bond distances ranging from 1.95–2.06 Å. In the fourth Cu3+ site, Cu3+ is bonded to five O2- atoms to form CuO5 square pyramids that share corners with four CuO6 octahedra and edges with two equivalent CuO5 square pyramids. The corner-sharing octahedra tilt angles range from 52–55°. There are a spread of Cu–O bond distances ranging from 1.91–2.07 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ca2+ and three Cu3+ atoms. In the second O2- site, O2- is bonded to one Ca2+ and three Cu3+ atoms to form distorted OCaCu3 trigonal pyramids that share corners with two equivalent OCa2Cu3 square pyramids, corners with two equivalent OCaCu3 trigonal pyramids, and edges with three OCa2Cu3 square pyramids. In the third O2- site, O2- is bonded to one Ca2+ and three Cu3+ atoms to form distorted OCaCu3 trigonal pyramids that share corners with two equivalent OCa2Cu3 square pyramids, corners with two equivalent OCaCu3 trigonal pyramids, and edges with three OCa2Cu3 square pyramids. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ca2+ and three Cu3+ atoms. In the fifth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two equivalent Ca2+ and two equivalent Cu3+ atoms. In the sixth O2- site, O2- is bonded to two equivalent Ca2+ and three Cu3+ atoms to form OCa2Cu3 square pyramids that share corners with two equivalent OCaCu3 trigonal pyramids, edges with four OCa2Cu3 square pyramids, and edges with three OCaCu3 trigonal pyramids. In the seventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to two equivalent Ca2+ and two equivalent Cu3+ atoms. In the eighth O2- site, O2- is bonded to two equivalent Ca2+ and three Cu3+ atoms to form OCa2Cu3 square pyramids that share corners with two equivalent OCaCu3 trigonal pyramids, edges with four OCa2Cu3 square pyramids, and edges with three OCaCu3 trigonal pyramids.