Materials Data on KNaMg5(Si2O5)6 by Materials Project

KNaMg5(Si2O5)6 crystallizes in the hexagonal P-62c space group. The structure is three-dimensional. K1+ is bonded in a 12-coordinate geometry to twelve O2- atoms. There are six shorter (2.94 Å) and six longer (3.07 Å) K–O bond lengths. Na1+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are three shorter (2.65 Å) and six longer (2.96 Å) Na–O bond lengths. There are two inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded in a distorted rectangular see-saw-like geometry to four O2- atoms. There is two shorter (1.97 Å) and two longer (2.01 Å) Mg–O bond length. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six SiO4 tetrahedra. There are three shorter (2.10 Å) and three longer (2.16 Å) Mg–O bond lengths. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one MgO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 39°. There is one shorter (1.61 Å) and three longer (1.64 Å) Si–O bond length. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one MgO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 41°. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to one K1+ and two Si4+ atoms. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to one K1+ and two Si4+ atoms. In the third O2- site, O2- is bonded in a 2-coordinate geometry to one Na1+ and two equivalent Si4+ atoms. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, two Mg2+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a linear geometry to two equivalent Si4+ atoms. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Mg2+ and one Si4+ atom.