Materials Data on KCa7Si3(O4F)3 by Materials Project
KCa7Si3(O4F)3 crystallizes in the trigonal P31c space group. The structure is three-dimensional. K1+ is bonded in a 12-coordinate geometry to nine O2- and three equivalent F1- atoms. There are a spread of K–O bond distances ranging from 2.87–3.32 Å. All K–F bond lengths are 2.68 Å. There are three inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to six equivalent O2- atoms to form distorted CaO6 pentagonal pyramids that share corners with six equivalent SiO4 tetrahedra and faces with two equivalent CaO6 pentagonal pyramids. There are three shorter (2.38 Å) and three longer (2.45 Å) Ca–O bond lengths. In the second Ca2+ site, Ca2+ is bonded in a 8-coordinate geometry to six O2- and two equivalent F1- atoms. There are a spread of Ca–O bond distances ranging from 2.31–2.91 Å. There are one shorter (2.32 Å) and one longer (2.36 Å) Ca–F bond lengths. In the third Ca2+ site, Ca2+ is bonded in a 8-coordinate geometry to six O2- and two equivalent F1- atoms. There are a spread of Ca–O bond distances ranging from 2.33–2.74 Å. There are one shorter (2.39 Å) and one longer (2.54 Å) Ca–F bond lengths. Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with two equivalent CaO6 pentagonal pyramids. There is three shorter (1.65 Å) and one longer (1.66 Å) Si–O bond length. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to one K1+, four Ca2+, and one Si4+ atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one Si4+ atom. In the third O2- site, O2- is bonded in a 1-coordinate geometry to one K1+, three Ca2+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to one K1+, four Ca2+, and one Si4+ atom. F1- is bonded to one K1+ and four Ca2+ atoms to form a mixture of distorted edge and corner-sharing FKCa4 square pyramids.