DOI: 10.17188/1192525
title: Materials Data on Na2Al2As3 by Materials Project

description: Na2Al2As3 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are four inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to six As+2.67- atoms to form distorted NaAs6 octahedra that share corners with eight AlAs4 tetrahedra, corners with five NaAs5 trigonal bipyramids, an edgeedge with one NaAs6 octahedra, edges with four AlAs4 tetrahedra, and edges with two NaAs5 trigonal bipyramids. There are a spread of Na–As bond distances ranging from 3.01–3.32 Å. In the second Na1+ site, Na1+ is bonded to five As+2.67- atoms to form distorted NaAs5 trigonal bipyramids that share a cornercorner with one NaAs6 octahedra, corners with six AlAs4 tetrahedra, a cornercorner with one NaAs5 trigonal bipyramid, an edgeedge with one NaAs6 octahedra, edges with four AlAs4 tetrahedra, and edges with two NaAs5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 83°. There are a spread of Na–As bond distances ranging from 3.04–3.20 Å. In the third Na1+ site, Na1+ is bonded to five As+2.67- atoms to form distorted NaAs5 trigonal bipyramids that share corners with four equivalent NaAs6 octahedra, corners with seven AlAs4 tetrahedra, a cornercorner with one NaAs5 trigonal bipyramid, an edgeedge with one NaAs6 octahedra, edges with three AlAs4 tetrahedra, and edges with two NaAs5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 32–105°. There are a spread of Na–As bond distances ranging from 3.07–3.29 Å. In the fourth Na1+ site, Na1+ is bonded in a 5-coordinate geometry to five As+2.67- atoms. There are a spread of Na–As bond distances ranging from 2.86–3.31 Å. There are four inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four As+2.67- atoms to form AlAs4 tetrahedra that share a cornercorner with one NaAs6 octahedra, corners with five AlAs4 tetrahedra, corners with five NaAs5 trigonal bipyramids, an edgeedge with one NaAs6 octahedra, an edgeedge with one AlAs4 tetrahedra, and an edgeedge with one NaAs5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 23°. There are a spread of Al–As bond distances ranging from 2.47–2.60 Å. In the second Al3+ site, Al3+ is bonded to four As+2.67- atoms to form AlAs4 tetrahedra that share corners with two equivalent NaAs6 octahedra, corners with five AlAs4 tetrahedra, corners with two NaAs5 trigonal bipyramids, edges with two equivalent NaAs6 octahedra, an edgeedge with one AlAs4 tetrahedra, and edges with two equivalent NaAs5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 28–60°. There are a spread of Al–As bond distances ranging from 2.49–2.51 Å. In the third Al3+ site, Al3+ is bonded to four As+2.67- atoms to form AlAs4 tetrahedra that share corners with three equivalent NaAs6 octahedra, corners with five AlAs4 tetrahedra, corners with three NaAs5 trigonal bipyramids, an edgeedge with one NaAs6 octahedra, an edgeedge with one AlAs4 tetrahedra, and edges with two NaAs5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 5–57°. There are a spread of Al–As bond distances ranging from 2.47–2.55 Å. In the fourth Al3+ site, Al3+ is bonded to four As+2.67- atoms to form AlAs4 tetrahedra that share corners with two equivalent NaAs6 octahedra, corners with five AlAs4 tetrahedra, corners with three NaAs5 trigonal bipyramids, an edgeedge with one AlAs4 tetrahedra, and edges with two equivalent NaAs5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 27–35°. There are a spread of Al–As bond distances ranging from 2.50–2.55 Å. There are six inequivalent As+2.67- sites. In the first As+2.67- site, As+2.67- is bonded in a 6-coordinate geometry to three Na1+ and three Al3+ atoms. In the second As+2.67- site, As+2.67- is bonded to four Na1+ and three Al3+ atoms to form distorted edge-sharing AsNa4Al3 pentagonal bipyramids. In the third As+2.67- site, As+2.67- is bonded to four Na1+ and three Al3+ atoms to form distorted edge-sharing AsNa4Al3 pentagonal bipyramids. In the fourth As+2.67- site, As+2.67- is bonded in a 7-coordinate geometry to four Na1+, two Al3+, and one As+2.67- atom. The As–As bond length is 2.54 Å. In the fifth As+2.67- site, As+2.67- is bonded in a 6-coordinate geometry to three Na1+ and three Al3+ atoms. In the sixth As+2.67- site, As+2.67- is bonded in a 6-coordinate geometry to three Na1+, two Al3+, and one As+2.67- atom.