DOE OSTI2020
BaO2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent Ba sites. In the first Ba site, Ba is bonded in a 11-coordinate geometry to eleven O atoms. There are a spread of Ba–O bond distances ranging from 2.63–3.12 Å. In the second Ba site, Ba is bonded in a 11-coordinate geometry to eleven O atoms. There are a spread of Ba–O bond distances ranging from 2.62–3.42 Å. There are four inequivalent O sites. In the first O site, O is bonded to five Ba atoms to form OBa5 trigonal bipyramids that share corners with six equivalent OBa6 octahedra, corners with eight OBa5 trigonal bipyramids, edges with six OBa5 trigonal bipyramids, and faces with three equivalent OBa6 octahedra. The corner-sharing octahedra tilt angles range from 24–66°. In the second O site, O is bonded to five Ba atoms to form OBa5 trigonal bipyramids that share corners with six equivalent OBa6 octahedra, corners with eight OBa5 trigonal bipyramids, edges with six OBa5 trigonal bipyramids, and faces with three equivalent OBa6 octahedra. The corner-sharing octahedra tilt angles range from 24–69°. In the third O site, O is bonded in a 6-coordinate geometry to six Ba atoms. In the fourth O site, O is bonded to six Ba atoms to form distorted OBa6 octahedra that share corners with eight equivalent OBa6 octahedra, corners with twelve OBa5 trigonal bipyramids, edges with two equivalent OBa6 octahedra, and faces with six OBa5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 42–62°.