Materials Data on Na2MgFeF7 by Materials Project

Abstract

Na2MgFeF7 crystallizes in the orthorhombic Imm2 space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to eight F1- atoms to form distorted NaF8 hexagonal bipyramids that share corners with two equivalent NaF8 hexagonal bipyramids, corners with two equivalent FeF6 octahedra, edges with two equivalent FeF6 octahedra, and edges with four equivalent MgF6 octahedra. The corner-sharing octahedra tilt angles range from 54–55°. There are a spread of Na–F bond distances ranging from 2.25–2.88 Å. In the second Na1+ site, Na1+ is bonded in a distorted body-centered cubic geometry to eight F1- atoms. There are four shorter (2.45 Å) and four longer (2.80 Å) Na–F bond lengths. Mg2+ is bonded to six F1- atoms to form MgF6 octahedra that share corners with two equivalent MgF6 octahedra, corners with four equivalent FeF6 octahedra, and edges with four equivalent NaF8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 41–43°. There is two shorter (1.96 Å) and four longer (2.00 Å) Mg–F bond length. Fe3+ is bonded to six F1- atoms to form FeF6 octahedra that share corners with two equivalent NaF8 hexagonal bipyramids, corners with four equivalent MgF6 octahedra, and edges with two equivalent NaF8 hexagonal bipyramids. The corner-sharing octahedral tilt angles are 41°. There are a spread of Fe–F bond distances ranging from 1.94–1.98 Å. There are six inequivalent F1- sites. In the first F1- site, F1- is bonded to three Na1+ and one Fe3+ atom to form a mixture of distorted edge and corner-sharing FNa3Fe tetrahedra. In the second F1- site, F1- is bonded in a 4-coordinate geometry to two Na1+, one Mg2+, and one Fe3+ atom. In the third F1- site, F1- is bonded in a 4-coordinate geometry to two Na1+, one Mg2+, and one Fe3+ atom. In the fourth F1- site, F1- is bonded in a 2-coordinate geometry to two equivalent Na1+ and two equivalent Mg2+ atoms. In the fifth F1- site, F1- is bonded to three Na1+ and one Fe3+ atom to form a mixture of distorted edge and corner-sharing FNa3Fe tetrahedra. In the sixth F1- site, F1- is bonded in a 2-coordinate geometry to two equivalent Na1+ and two equivalent Mg2+ atoms.