DOE OSTI2020
Ca2H3Br crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Ca2+ is bonded in a 4-coordinate geometry to seven H1- and three equivalent Br1- atoms. There are a spread of Ca–H bond distances ranging from 2.27–2.59 Å. All Ca–Br bond lengths are 3.14 Å. There are two inequivalent H1- sites. In the first H1- site, H1- is bonded to four equivalent Ca2+ atoms to form HCa4 trigonal pyramids that share corners with three equivalent HCa6 octahedra, corners with six equivalent BrCa6 octahedra, corners with six equivalent HCa4 trigonal pyramids, edges with three equivalent BrCa6 octahedra, edges with three equivalent HCa4 trigonal pyramids, and faces with three equivalent HCa6 octahedra. The corner-sharing octahedra tilt angles range from 36–46°. In the second H1- site, H1- is bonded to six equivalent Ca2+ atoms to form HCa6 octahedra that share corners with twelve equivalent BrCa6 octahedra, corners with six equivalent HCa4 trigonal pyramids, edges with six equivalent HCa6 octahedra, faces with two equivalent BrCa6 octahedra, and faces with six equivalent HCa4 trigonal pyramids. The corner-sharing octahedral tilt angles are 49°. Br1- is bonded to six equivalent Ca2+ atoms to form distorted BrCa6 octahedra that share corners with twelve equivalent HCa6 octahedra, corners with twelve equivalent HCa4 trigonal pyramids, edges with six equivalent BrCa6 octahedra, edges with six equivalent HCa4 trigonal pyramids, and faces with two equivalent HCa6 octahedra. The corner-sharing octahedral tilt angles are 49°.