DOI: 10.17188/1696632
title: Materials Data on Ca2CdAs2 by Materials Project

description: Ca2CdAs2 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are ten inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to five As3- atoms to form distorted CaAs5 trigonal bipyramids that share corners with two equivalent CaAs6 octahedra, corners with four CaAs5 square pyramids, corners with three CdAs4 tetrahedra, corners with four CaAs5 trigonal bipyramids, an edgeedge with one CaAs6 octahedra, edges with two CaAs5 square pyramids, edges with four CdAs4 tetrahedra, and edges with three CaAs5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 35°. There are a spread of Ca–As bond distances ranging from 2.93–3.10 Å. In the second Ca2+ site, Ca2+ is bonded to six As3- atoms to form CaAs6 octahedra that share a cornercorner with one CaAs6 octahedra, corners with seven CaAs5 square pyramids, corners with three CdAs4 tetrahedra, corners with two equivalent CaAs5 trigonal bipyramids, edges with four CaAs6 octahedra, edges with three CdAs4 tetrahedra, edges with three CaAs5 trigonal bipyramids, and a faceface with one CaAs5 square pyramid. The corner-sharing octahedral tilt angles are 8°. There are a spread of Ca–As bond distances ranging from 3.08–3.40 Å. In the third Ca2+ site, Ca2+ is bonded to five As3- atoms to form CaAs5 square pyramids that share corners with four CaAs6 octahedra, corners with five CdAs4 tetrahedra, corners with six CaAs5 trigonal bipyramids, edges with four CaAs5 square pyramids, an edgeedge with one CdAs4 tetrahedra, an edgeedge with one CaAs5 trigonal bipyramid, and a faceface with one CaAs6 octahedra. The corner-sharing octahedra tilt angles range from 45–55°. There are a spread of Ca–As bond distances ranging from 2.94–3.06 Å. In the fourth Ca2+ site, Ca2+ is bonded to six As3- atoms to form CaAs6 octahedra that share corners with six CaAs5 square pyramids, corners with six CdAs4 tetrahedra, corners with three CaAs5 trigonal bipyramids, edges with six CaAs6 octahedra, edges with three CdAs4 tetrahedra, an edgeedge with one CaAs5 trigonal bipyramid, and a faceface with one CaAs5 square pyramid. There are a spread of Ca–As bond distances ranging from 3.06–3.32 Å. In the fifth Ca2+ site, Ca2+ is bonded to five As3- atoms to form distorted CaAs5 trigonal bipyramids that share corners with three CaAs6 octahedra, corners with five CaAs5 square pyramids, corners with two equivalent CdAs4 tetrahedra, corners with two equivalent CaAs5 trigonal bipyramids, an edgeedge with one CaAs6 octahedra, an edgeedge with one CaAs5 square pyramid, edges with five CdAs4 tetrahedra, and edges with two equivalent CaAs5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 36–52°. There are a spread of Ca–As bond distances ranging from 3.04–3.18 Å. In the sixth Ca2+ site, Ca2+ is bonded to five As3- atoms to form CaAs5 square pyramids that share corners with six CaAs6 octahedra, corners with two equivalent CaAs5 square pyramids, corners with two equivalent CdAs4 tetrahedra, corners with three CaAs5 trigonal bipyramids, an edgeedge with one CaAs6 octahedra, edges with three CaAs5 square pyramids, edges with four CdAs4 tetrahedra, an edgeedge with one CaAs5 trigonal bipyramid, and a faceface with one CaAs6 octahedra. The corner-sharing octahedra tilt angles range from 33–50°. There are a spread of Ca–As bond distances ranging from 2.96–3.05 Å. In the seventh Ca2+ site, Ca2+ is bonded to five As3- atoms to form distorted CaAs5 trigonal bipyramids that share a cornercorner with one CaAs6 octahedra, corners with seven CaAs5 square pyramids, corners with two equivalent CdAs4 tetrahedra, corners with two equivalent CaAs5 trigonal bipyramids, edges with two equivalent CaAs6 octahedra, edges with two CaAs5 square pyramids, edges with four CdAs4 tetrahedra, and edges with three CaAs5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 11°. There are a spread of Ca–As bond distances ranging from 2.94–3.20 Å. In the eighth Ca2+ site, Ca2+ is bonded to five As3- atoms to form distorted CaAs5 square pyramids that share corners with six CaAs6 octahedra, corners with six CdAs4 tetrahedra, corners with three CaAs5 trigonal bipyramids, edges with four CaAs5 square pyramids, an edgeedge with one CdAs4 tetrahedra, an edgeedge with one CaAs5 trigonal bipyramid, and a faceface with one CaAs6 octahedra. The corner-sharing octahedra tilt angles range from 44–53°. There are a spread of Ca–As bond distances ranging from 3.00–3.28 Å. In the ninth Ca2+ site, Ca2+ is bonded to six As3- atoms to form distorted CaAs6 octahedra that share a cornercorner with one CaAs6 octahedra, corners with eight CaAs5 square pyramids, corners with six CdAs4 tetrahedra, a cornercorner with one CaAs5 trigonal bipyramid, edges with four CaAs6 octahedra, an edgeedge with one CaAs5 square pyramid, edges with three CdAs4 tetrahedra, and faces with two CaAs5 square pyramids. The corner-sharing octahedral tilt angles are 8°. There are a spread of Ca–As bond distances ranging from 2.97–3.52 Å. In the tenth Ca2+ site, Ca2+ is bonded to five As3- atoms to form CaAs5 square pyramids that share corners with five CaAs6 octahedra, corners with two equivalent CaAs5 square pyramids, corners with four CdAs4 tetrahedra, corners with four CaAs5 trigonal bipyramids, edges with three CaAs5 square pyramids, edges with four CdAs4 tetrahedra, edges with two CaAs5 trigonal bipyramids, and a faceface with one CaAs6 octahedra. The corner-sharing octahedra tilt angles range from 50–59°. There are one shorter (2.95 Å) and four longer (3.02 Å) Ca–As bond lengths. There are five inequivalent Cd2+ sites. In the first Cd2+ site, Cd2+ is bonded to four As3- atoms to form CdAs4 tetrahedra that share corners with two equivalent CaAs6 octahedra, corners with four CaAs5 square pyramids, corners with five CdAs4 tetrahedra, a cornercorner with one CaAs5 trigonal bipyramid, edges with three CaAs6 octahedra, an edgeedge with one CaAs5 square pyramid, and edges with two equivalent CaAs5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 22°. There are a spread of Cd–As bond distances ranging from 2.67–2.81 Å. In the second Cd2+ site, Cd2+ is bonded to four As3- atoms to form CdAs4 tetrahedra that share corners with two equivalent CaAs6 octahedra, corners with six CaAs5 square pyramids, corners with four CdAs4 tetrahedra, edges with two equivalent CaAs6 octahedra, edges with three CaAs5 square pyramids, and edges with two equivalent CaAs5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 45°. There are a spread of Cd–As bond distances ranging from 2.65–2.89 Å. In the third Cd2+ site, Cd2+ is bonded to four As3- atoms to form CdAs4 tetrahedra that share corners with six CaAs6 octahedra, corners with five CdAs4 tetrahedra, corners with two equivalent CaAs5 trigonal bipyramids, an edgeedge with one CaAs6 octahedra, edges with four CaAs5 square pyramids, and edges with two equivalent CaAs5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 27–68°. There are a spread of Cd–As bond distances ranging from 2.69–2.88 Å. In the fourth Cd2+ site, Cd2+ is bonded to four As3- atoms to form CdAs4 tetrahedra that share a cornercorner with one CaAs6 octahedra, corners with five CaAs5 square pyramids, corners with six CdAs4 tetrahedra, corners with two equivalent CaAs5 trigonal bipyramids, and edges with five CaAs5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 44°. There are a spread of Cd–As bond distances ranging from 2.70–2.95 Å. In the fifth Cd2+ site, Cd2+ is bonded to four As3- atoms to form CdAs4 tetrahedra that share corners with four CaAs6 octahedra, corners with two equivalent CaAs5 square pyramids, corners with four CdAs4 tetrahedra, corners with two equivalent CaAs5 trigonal bipyramids, edges with three CaAs6 octahedra, edges with two equivalent CaAs5 square pyramids, and edges with two equivalent CaAs5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 23–66°. There are a spread of Cd–As bond distances ranging from 2.70–3.05 Å. There are ten inequivalent As3- sites. In the first As3- site, As3- is bonded in a 6-coordinate geometry to three Ca2+ and three Cd2+ atoms. In the second As3- site, As3- is bonded in a 7-coordinate geometry to five Ca2+ and two equivalent Cd2+ atoms. In the third As3- site, As3- is bonded in a 8-coordinate geometry to six Ca2+ and two Cd2+ atoms. In the fourth As3- site, As3- is bonded in a 7-coordinate geometry to six Ca2+ and one Cd2+ atom. In the fifth As3- site, As3- is bonded in a 8-coordinate geometry to six Ca2+ and two Cd2+ atoms. In the sixth As3- site, As3- is bonded in a 9-coordinate geometry to six Ca2+ and three Cd2+ atoms. In the seventh As3- site, As3- is bonded in a 7-coordinate geometry to five Ca2+ and two equivalent Cd2+ atoms. In the eighth As3- site, As3- is bonded to six Ca2+ and one Cd2+ atom to form distorted AsCa6Cd pentagonal bipyramids that share corners with two equivalent AsCa5Cd2 pentagonal bipyramids, an edgeedge with one AsCa5Cd2 pentagonal bipyramid, and faces with two equivalent AsCa6Cd pentagonal bipyramids. In the ninth As3- site, As3- is bonded to five Ca2+ and two equivalent Cd2+ atoms to form a mixture of distorted edge and corner-sharing AsCa5Cd2 pentagonal bipyramids. In the tenth As3- site, As3- is bonded in a 7-coordinate geometry to five Ca2+ and two equivalent Cd2+ atoms.