Materials Data on Na3Ca3AlAs4 by Materials Project
Na3Ca3AlAs4 crystallizes in the hexagonal P6_3mc space group. The structure is three-dimensional. Na1+ is bonded to four As3- atoms to form distorted NaAs4 trigonal pyramids that share corners with two equivalent AlAs4 tetrahedra, corners with eight equivalent NaAs4 trigonal pyramids, and an edgeedge with one AlAs4 tetrahedra. There are a spread of Na–As bond distances ranging from 2.88–3.24 Å. Ca2+ is bonded in a 6-coordinate geometry to six As3- atoms. There are a spread of Ca–As bond distances ranging from 3.04–3.56 Å. Al3+ is bonded to four As3- atoms to form AlAs4 tetrahedra that share corners with six equivalent NaAs4 trigonal pyramids and edges with three equivalent NaAs4 trigonal pyramids. There are three shorter (2.47 Å) and one longer (2.53 Å) Al–As bond lengths. There are two inequivalent As3- sites. In the first As3- site, As3- is bonded in a 8-coordinate geometry to three equivalent Na1+, four equivalent Ca2+, and one Al3+ atom. In the second As3- site, As3- is bonded in a 7-coordinate geometry to three equivalent Na1+, six equivalent Ca2+, and one Al3+ atom.