Materials Data on Ca4As3 by Materials Project
Ca4As3 crystallizes in the orthorhombic Pbam space group. The structure is three-dimensional. there are six inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to six As+2.67- atoms to form distorted CaAs6 octahedra that share corners with four equivalent CaAs6 octahedra, corners with two equivalent CaAs4 trigonal pyramids, an edgeedge with one CaAs6 octahedra, and an edgeedge with one CaAs4 trigonal pyramid. The corner-sharing octahedra tilt angles range from 38–58°. There are a spread of Ca–As bond distances ranging from 2.93–3.45 Å. In the second Ca2+ site, Ca2+ is bonded in a 5-coordinate geometry to five As+2.67- atoms. There are a spread of Ca–As bond distances ranging from 2.91–3.26 Å. In the third Ca2+ site, Ca2+ is bonded to four As+2.67- atoms to form distorted CaAs4 trigonal pyramids that share corners with four equivalent CaAs6 octahedra, edges with two equivalent CaAs6 octahedra, and an edgeedge with one CaAs4 trigonal pyramid. The corner-sharing octahedra tilt angles range from 53–87°. There are a spread of Ca–As bond distances ranging from 2.86–3.03 Å. In the fourth Ca2+ site, Ca2+ is bonded in a 6-coordinate geometry to six As+2.67- atoms. There are a spread of Ca–As bond distances ranging from 3.01–3.56 Å. In the fifth Ca2+ site, Ca2+ is bonded in a 6-coordinate geometry to six As+2.67- atoms. There are a spread of Ca–As bond distances ranging from 2.91–3.34 Å. In the sixth Ca2+ site, Ca2+ is bonded in a distorted see-saw-like geometry to four As+2.67- atoms. There are two shorter (2.90 Å) and two longer (3.06 Å) Ca–As bond lengths. There are five inequivalent As+2.67- sites. In the first As+2.67- site, As+2.67- is bonded in a 7-coordinate geometry to seven Ca2+ atoms. In the second As+2.67- site, As+2.67- is bonded in a 7-coordinate geometry to six Ca2+ and one As+2.67- atom. The As–As bond length is 2.54 Å. In the third As+2.67- site, As+2.67- is bonded to six Ca2+ atoms to form distorted edge-sharing AsCa6 pentagonal pyramids. In the fourth As+2.67- site, As+2.67- is bonded in a 8-coordinate geometry to eight Ca2+ atoms. In the fifth As+2.67- site, As+2.67- is bonded in a 9-coordinate geometry to eight Ca2+ and one As+2.67- atom. The As–As bond length is 2.56 Å.