Materials Data on KNaFe(Si2O5)2 by Materials Project

Abstract

KNaFe(Si2O5)2 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. K1+ is bonded in a 8-coordinate geometry to nine O2- atoms. There are a spread of K–O bond distances ranging from 2.78–3.46 Å. Na1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Na–O bond distances ranging from 2.42–2.72 Å. Fe2+ is bonded to five O2- atoms to form FeO5 trigonal bipyramids that share corners with five SiO4 tetrahedra and an edgeedge with one FeO5 trigonal bipyramid. There are a spread of Fe–O bond distances ranging from 2.03–2.30 Å. There are four inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three SiO4 tetrahedra and a cornercorner with one FeO5 trigonal bipyramid. There are a spread of Si–O bond distances ranging from 1.60–1.66 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three SiO4 tetrahedra and a cornercorner with one FeO5 trigonal bipyramid. There are a spread of Si–O bond distances ranging from 1.60–1.65 Å. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three SiO4 tetrahedra and a cornercorner with one FeO5 trigonal bipyramid. There is one shorter (1.60 Å) and three longer (1.65 Å) Si–O bond length. In the fourth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three SiO4 tetrahedra and corners with two equivalent FeO5 trigonal bipyramids. There is one shorter (1.60 Å) and three longer (1.65 Å) Si–O bond length. There are ten inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, two equivalent Fe2+, and one Si4+ atom. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the third O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one K1+ and two Si4+ atoms. In the fourth O2- site, O2- is bonded to two equivalent Na1+, one Fe2+, and one Si4+ atom to form distorted edge-sharing ONa2FeSi trigonal pyramids. In the fifth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+ and two Si4+ atoms. In the sixth O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent K1+ and two Si4+ atoms. In the seventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one K1+ and two Si4+ atoms. In the eighth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two equivalent K1+ and two Si4+ atoms. In the ninth O2- site, O2- is bonded in a 3-coordinate geometry to one K1+, one Na1+, one Fe2+, and one Si4+ atom. In the tenth O2- site, O2- is bonded in a 4-coordinate geometry to one K1+, one Na1+, one Fe2+, and one Si4+ atom.