DOI: 10.17188/1192684
title: Materials Data on NaMg4(AsO4)3 by Materials Project

description: NaMg4(AsO4)3 crystallizes in the tetragonal I-42d space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are four shorter (2.36 Å) and four longer (2.73 Å) Na–O bond lengths. In the second Na1+ site, Na1+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are four shorter (2.36 Å) and four longer (2.73 Å) Na–O bond lengths. There are four inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two MgO6 octahedra, corners with four AsO4 tetrahedra, edges with two MgO6 octahedra, and an edgeedge with one AsO4 tetrahedra. The corner-sharing octahedral tilt angles are 56°. There are a spread of Mg–O bond distances ranging from 2.05–2.16 Å. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent MgO6 octahedra, corners with four AsO4 tetrahedra, edges with two equivalent MgO6 octahedra, and an edgeedge with one AsO4 tetrahedra. The corner-sharing octahedral tilt angles are 56°. There are a spread of Mg–O bond distances ranging from 2.05–2.16 Å. In the third Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent MgO6 octahedra, corners with six AsO4 tetrahedra, and edges with two equivalent MgO6 octahedra. The corner-sharing octahedral tilt angles are 56°. There are a spread of Mg–O bond distances ranging from 2.10–2.19 Å. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent MgO6 octahedra, corners with six AsO4 tetrahedra, and edges with two equivalent MgO6 octahedra. The corner-sharing octahedral tilt angles are 56°. There are a spread of Mg–O bond distances ranging from 2.10–2.19 Å. There are four inequivalent As5+ sites. In the first As5+ site, As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share corners with six MgO6 octahedra and an edgeedge with one MgO6 octahedra. The corner-sharing octahedra tilt angles range from 47–49°. There is two shorter (1.72 Å) and two longer (1.74 Å) As–O bond length. In the second As5+ site, As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share corners with six MgO6 octahedra and an edgeedge with one MgO6 octahedra. The corner-sharing octahedra tilt angles range from 47–49°. There is two shorter (1.72 Å) and two longer (1.74 Å) As–O bond length. In the third As5+ site, As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share corners with six MgO6 octahedra and an edgeedge with one MgO6 octahedra. The corner-sharing octahedra tilt angles range from 47–49°. There is two shorter (1.72 Å) and two longer (1.74 Å) As–O bond length. In the fourth As5+ site, As5+ is bonded to four equivalent O2- atoms to form AsO4 tetrahedra that share corners with eight MgO6 octahedra. The corner-sharing octahedra tilt angles range from 49–50°. All As–O bond lengths are 1.72 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to two Mg2+ and one As5+ atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, two Mg2+, and one As5+ atom. In the third O2- site, O2- is bonded to one Na1+, two Mg2+, and one As5+ atom to form a mixture of distorted edge and corner-sharing ONaMg2As tetrahedra.