Materials Data on BaCaO2 by Materials Project

Abstract

BaCaO2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ba2+ is bonded to seven O2- atoms to form distorted BaO7 pentagonal bipyramids that share corners with four equivalent BaO7 pentagonal bipyramids, corners with three equivalent CaO5 trigonal bipyramids, edges with four equivalent BaO7 pentagonal bipyramids, edges with seven equivalent CaO5 trigonal bipyramids, and faces with two equivalent BaO7 pentagonal bipyramids. There are a spread of Ba–O bond distances ranging from 2.76–2.98 Å. Ca2+ is bonded to five O2- atoms to form CaO5 trigonal bipyramids that share corners with three equivalent BaO7 pentagonal bipyramids, corners with four equivalent CaO5 trigonal bipyramids, edges with seven equivalent BaO7 pentagonal bipyramids, and edges with two equivalent CaO5 trigonal bipyramids. There are a spread of Ca–O bond distances ranging from 2.31–2.48 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to three equivalent Ba2+ and three equivalent Ca2+ atoms to form distorted OBa3Ca3 octahedra that share corners with nine equivalent OBa4Ca2 octahedra, edges with nine OBa3Ca3 octahedra, and a faceface with one OBa4Ca2 octahedra. The corner-sharing octahedra tilt angles range from 8–60°. In the second O2- site, O2- is bonded to four equivalent Ba2+ and two equivalent Ca2+ atoms to form a mixture of corner, edge, and face-sharing OBa4Ca2 octahedra. The corner-sharing octahedra tilt angles range from 8–60°.