Materials Data on Na8TiAs4 by Materials Project

Abstract

Na8TiAs4 crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to six equivalent As3- atoms to form NaAs6 octahedra that share corners with eighteen equivalent NaAs4 tetrahedra, edges with six equivalent NaAs6 octahedra, faces with two equivalent TiAs4 tetrahedra, and faces with six equivalent NaAs4 tetrahedra. All Na–As bond lengths are 3.21 Å. In the second Na1+ site, Na1+ is bonded to four equivalent As3- atoms to form distorted NaAs4 tetrahedra that share corners with six equivalent NaAs6 octahedra, corners with two equivalent TiAs4 tetrahedra, corners with twelve equivalent NaAs4 tetrahedra, an edgeedge with one TiAs4 tetrahedra, edges with four equivalent NaAs4 tetrahedra, and faces with two equivalent NaAs6 octahedra. The corner-sharing octahedra tilt angles range from 33–51°. There are two shorter (3.03 Å) and two longer (3.17 Å) Na–As bond lengths. Ti4+ is bonded to four equivalent As3- atoms to form TiAs4 tetrahedra that share corners with twelve equivalent NaAs4 tetrahedra, edges with six equivalent NaAs4 tetrahedra, and faces with four equivalent NaAs6 octahedra. All Ti–As bond lengths are 2.52 Å. As3- is bonded in a 10-coordinate geometry to nine Na1+ and one Ti4+ atom.