DOI: 10.17188/1666589
title: Materials Data on KMg3AlSi3(O5F)2 by Materials Project

description: KMg3AlSi3O10F2 is Esseneite-derived structured and crystallizes in the triclinic P1 space group. The structure is two-dimensional and consists of one KMg3AlSi3O10F2 sheet oriented in the (0, 0, 1) direction. K1+ is bonded in a 3-coordinate geometry to three O2- atoms. There are two shorter (2.73 Å) and one longer (2.74 Å) K–O bond lengths. There are three inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- and two F1- atoms to form MgO4F2 octahedra that share a cornercorner with one AlO4 tetrahedra, corners with three SiO4 tetrahedra, and edges with six MgO4F2 octahedra. There are a spread of Mg–O bond distances ranging from 2.01–2.17 Å. There are one shorter (2.03 Å) and one longer (2.07 Å) Mg–F bond lengths. In the second Mg2+ site, Mg2+ is bonded to four O2- and two F1- atoms to form MgO4F2 octahedra that share a cornercorner with one AlO4 tetrahedra, corners with three SiO4 tetrahedra, and edges with six MgO4F2 octahedra. There are a spread of Mg–O bond distances ranging from 2.02–2.13 Å. There are one shorter (2.03 Å) and one longer (2.12 Å) Mg–F bond lengths. In the third Mg2+ site, Mg2+ is bonded to four O2- and two F1- atoms to form MgO4F2 octahedra that share a cornercorner with one AlO4 tetrahedra, corners with three SiO4 tetrahedra, and edges with six MgO4F2 octahedra. There are a spread of Mg–O bond distances ranging from 2.02–2.17 Å. There are one shorter (2.03 Å) and one longer (2.06 Å) Mg–F bond lengths. Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three MgO4F2 octahedra and corners with three equivalent SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 61°. There is three shorter (1.75 Å) and one longer (1.77 Å) Al–O bond length. 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 three MgO4F2 octahedra and corners with three equivalent AlO4 tetrahedra. The corner-sharing octahedral tilt angles are 58°. There is three shorter (1.63 Å) and one longer (1.68 Å) Si–O bond length. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three MgO4F2 octahedra and corners with three equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 56–58°. There is one shorter (1.62 Å) and three longer (1.66 Å) Si–O bond length. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three MgO4F2 octahedra and corners with three equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 56–57°. There is one shorter (1.62 Å) and three longer (1.66 Å) Si–O bond length. There are ten inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Al3+, and one Si4+ atom. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two Si4+ atoms. In the third O2- site, O2- is bonded to three Mg2+ and one Al3+ atom to form distorted corner-sharing OMg3Al tetrahedra. In the fourth O2- site, O2- is bonded to three Mg2+ and one Si4+ atom to form distorted corner-sharing OMg3Si trigonal pyramids. In the fifth O2- site, O2- is bonded in a rectangular see-saw-like geometry to three Mg2+ and one Si4+ atom. In the sixth O2- site, O2- is bonded in a rectangular see-saw-like geometry to three Mg2+ and one Si4+ atom. In the seventh O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Al3+, and one Si4+ atom. In the eighth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Al3+, and one Si4+ atom. In the ninth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two Si4+ atoms. In the tenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two Si4+ atoms. There are two inequivalent F1- sites. In the first F1- site, F1- is bonded in a trigonal non-coplanar geometry to three Mg2+ atoms. In the second F1- site, F1- is bonded in a distorted T-shaped geometry to three Mg2+ atoms.