Materials Data on Na2Ca(AsO3)4 by Materials Project

Abstract

Na2Ca(AsO3)4 crystallizes in the tetragonal P4/nbm space group. The structure is three-dimensional. Na1+ is bonded to six O2- atoms to form NaO6 octahedra that share corners with eight equivalent AsO4 tetrahedra. There are four shorter (2.32 Å) and two longer (2.65 Å) Na–O bond lengths. Ca2+ is bonded in a 8-coordinate geometry to eight equivalent O2- atoms. All Ca–O bond lengths are 2.49 Å. As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share corners with four equivalent NaO6 octahedra and corners with two equivalent AsO4 tetrahedra. The corner-sharing octahedra tilt angles range from 48–72°. There is two shorter (1.67 Å) and two longer (1.81 Å) As–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to one Na1+ and two equivalent As5+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Ca2+, and one As5+ atom.