Materials Data on Na3CaMg3AlF14 by Materials Project

Abstract

Na3CaMg3AlF14 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Na1+ is bonded to eight F1- atoms to form distorted NaF8 hexagonal bipyramids that share edges with two equivalent CaF8 hexagonal bipyramids, edges with four equivalent NaF8 hexagonal bipyramids, edges with two equivalent AlF6 octahedra, and edges with four equivalent MgF6 octahedra. There are a spread of Na–F bond distances ranging from 2.23–2.66 Å. Ca2+ is bonded to eight F1- atoms to form distorted CaF8 hexagonal bipyramids that share edges with six equivalent NaF8 hexagonal bipyramids and edges with six equivalent MgF6 octahedra. There are two shorter (2.21 Å) and six longer (2.53 Å) Ca–F bond lengths. Mg2+ is bonded to six F1- atoms to form MgF6 octahedra that share corners with two equivalent AlF6 octahedra, corners with four equivalent MgF6 octahedra, edges with two equivalent CaF8 hexagonal bipyramids, and edges with four equivalent NaF8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 39–48°. There are four shorter (1.99 Å) and two longer (2.03 Å) Mg–F bond lengths. Al3+ is bonded to six equivalent F1- atoms to form AlF6 octahedra that share corners with six equivalent MgF6 octahedra and edges with six equivalent NaF8 hexagonal bipyramids. The corner-sharing octahedral tilt angles are 39°. All Al–F bond lengths are 1.83 Å. There are three inequivalent F1- sites. In the first F1- site, F1- is bonded to three equivalent Na1+ and one Ca2+ atom to form corner-sharing FNa3Ca tetrahedra. In the second F1- site, F1- is bonded in a 4-coordinate geometry to one Na1+, one Ca2+, and two equivalent Mg2+ atoms. In the third F1- site, F1- is bonded in a 2-coordinate geometry to two equivalent Na1+, one Mg2+, and one Al3+ atom.