Materials Data on K7Ta(SO4)6 by Materials Project
K7Ta(SO4)6 crystallizes in the trigonal R-3 space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to six equivalent O2- atoms to form KO6 octahedra that share corners with six equivalent SO4 tetrahedra and edges with six equivalent KO6 octahedra. All K–O bond lengths are 2.74 Å. In the second K1+ site, K1+ is bonded to six O2- atoms to form KO6 octahedra that share corners with two equivalent KO6 octahedra, corners with six equivalent SO4 tetrahedra, and edges with three KO6 octahedra. The corner-sharing octahedral tilt angles are 77°. There are a spread of K–O bond distances ranging from 2.72–2.98 Å. Ta5+ is bonded to six equivalent O2- atoms to form TaO6 octahedra that share corners with six equivalent SO4 tetrahedra. All Ta–O bond lengths are 1.98 Å. S6+ is bonded to four O2- atoms to form SO4 tetrahedra that share a cornercorner with one TaO6 octahedra and corners with seven KO6 octahedra. The corner-sharing octahedra tilt angles range from 28–64°. There are a spread of S–O bond distances ranging from 1.47–1.57 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent K1+ and one S6+ atom. In the second O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent K1+ and one S6+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to one Ta5+ and one S6+ atom. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to three K1+ and one S6+ atom.