Materials Data on K2Mg2Si2O7 by Materials Project
K2Mg2Si2O7 crystallizes in the trigonal P-31m space group. The structure is three-dimensional. K1+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are six shorter (2.77 Å) and three longer (2.97 Å) K–O bond lengths. Mg2+ is bonded to six equivalent O2- atoms to form MgO6 octahedra that share corners with six equivalent SiO4 tetrahedra and edges with three equivalent MgO6 octahedra. All Mg–O bond lengths are 2.15 Å. Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with six equivalent MgO6 octahedra and a cornercorner with one SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 55°. There is three shorter (1.65 Å) and one longer (1.72 Å) Si–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a linear geometry to six equivalent K1+ and two equivalent Si4+ atoms. In the second O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent K1+, two equivalent Mg2+, and one Si4+ atom.