Materials Data on K2SiF6 by Materials Project
K2SiF6 crystallizes in the hexagonal P6_3mc space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to twelve F1- atoms to form distorted KF12 cuboctahedra that share corners with six equivalent KF12 cuboctahedra, corners with three equivalent SiF6 octahedra, faces with eight KF12 cuboctahedra, and faces with three equivalent SiF6 octahedra. The corner-sharing octahedral tilt angles are 15°. There are a spread of K–F bond distances ranging from 2.91–3.14 Å. In the second K1+ site, K1+ is bonded to twelve F1- atoms to form distorted KF12 cuboctahedra that share corners with twelve equivalent KF12 cuboctahedra, faces with six equivalent KF12 cuboctahedra, and faces with four equivalent SiF6 octahedra. There are a spread of K–F bond distances ranging from 2.84–2.96 Å. Si4+ is bonded to six F1- atoms to form SiF6 octahedra that share corners with three equivalent KF12 cuboctahedra and faces with seven KF12 cuboctahedra. All Si–F bond lengths are 1.72 Å. There are two inequivalent F1- sites. In the first F1- site, F1- is bonded in a single-bond geometry to four K1+ and one Si4+ atom. In the second F1- site, F1- is bonded in a distorted single-bond geometry to four K1+ and one Si4+ atom.