Materials Data on Na2Th(AsO4)2 by Materials Project

Abstract

Na2Th(AsO4)2 is Esseneite-like structured and crystallizes in the orthorhombic Fddd space group. The structure is three-dimensional. Na1+ is bonded to six O2- atoms to form distorted NaO6 pentagonal pyramids that share corners with four equivalent AsO4 tetrahedra, edges with two equivalent NaO6 pentagonal pyramids, and an edgeedge with one AsO4 tetrahedra. There are a spread of Na–O bond distances ranging from 2.41–2.74 Å. Th4+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are four shorter (2.33 Å) and four longer (2.58 Å) Th–O bond lengths. As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share corners with four equivalent NaO6 pentagonal pyramids and an edgeedge with one NaO6 pentagonal pyramid. There is two shorter (1.71 Å) and two longer (1.73 Å) As–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Na1+, one Th4+, and one As5+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Th4+, and one As5+ atom.