DOI: 10.17188/1284017
title: Materials Data on KMg3AlSi3(O5F)2 by Materials Project

description: KMg3AlSi3O10F2 crystallizes in the monoclinic P2_1 space group. The structure is three-dimensional. K1+ is bonded in a 7-coordinate geometry to five O2- and two F1- atoms. There are a spread of K–O bond distances ranging from 2.65–3.00 Å. There are one shorter (2.63 Å) and one longer (3.22 Å) K–F bond lengths. There are three inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to three O2- and two F1- atoms to form distorted MgO3F2 trigonal bipyramids that share corners with four SiO4 tetrahedra and a cornercorner with one MgO3F trigonal pyramid. There are a spread of Mg–O bond distances ranging from 1.96–2.41 Å. There are one shorter (1.95 Å) and one longer (2.20 Å) Mg–F bond lengths. In the second Mg2+ site, Mg2+ is bonded in a 5-coordinate geometry to three O2- and two F1- atoms. There are a spread of Mg–O bond distances ranging from 1.93–2.30 Å. There are one shorter (1.87 Å) and one longer (2.16 Å) Mg–F bond lengths. In the third Mg2+ site, Mg2+ is bonded to three O2- and one F1- atom to form distorted MgO3F trigonal pyramids that share a cornercorner with one AlO4 tetrahedra, corners with three SiO4 tetrahedra, and a cornercorner with one MgO3F2 trigonal bipyramid. There are a spread of Mg–O bond distances ranging from 1.96–2.11 Å. The Mg–F bond length is 1.93 Å. Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three SiO4 tetrahedra and a cornercorner with one MgO3F trigonal pyramid. There are a spread of Al–O bond distances ranging from 1.72–1.82 Å. There are three inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with two equivalent AlO4 tetrahedra, corners with two SiO4 tetrahedra, and a cornercorner with one MgO3F2 trigonal bipyramid. There are a spread of Si–O bond distances ranging from 1.62–1.70 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra, corners with two SiO4 tetrahedra, a cornercorner with one MgO3F2 trigonal bipyramid, and a cornercorner with one MgO3F trigonal pyramid. There are a spread of Si–O bond distances ranging from 1.61–1.72 Å. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with two SiO4 tetrahedra, corners with two equivalent MgO3F2 trigonal bipyramids, and corners with two equivalent MgO3F trigonal pyramids. There are a spread of Si–O bond distances ranging from 1.59–1.73 Å. There are ten inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Mg2+, and one Si4+ atom. In the second O2- site, O2- is bonded in a bent 120 degrees geometry to one Al3+ and one Si4+ atom. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to one K1+ and two Si4+ atoms. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Al3+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to two Mg2+ and one Si4+ atom. In the sixth O2- site, O2- is bonded in a distorted T-shaped geometry to two Mg2+ and one Al3+ atom. In the seventh O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one K1+, one Al3+, and one Si4+ atom. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to one K1+, one Mg2+, and two Si4+ atoms. In the ninth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mg2+ and two Si4+ atoms. In the tenth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to two Mg2+ and one Si4+ atom. There are two inequivalent F1- sites. In the first F1- site, F1- is bonded in a 2-coordinate geometry to one K1+ and two Mg2+ atoms. In the second F1- site, F1- is bonded in a 3-coordinate geometry to one K1+ and three Mg2+ atoms.