Materials Data on K4CaU(Si2O7)2 by Materials Project
K4CaUSi4O14 crystallizes in the tetragonal P-4n2 space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 9-coordinate geometry to seven O2- atoms. There are a spread of K–O bond distances ranging from 2.97–3.21 Å. In the second K1+ site, K1+ is bonded in a 2-coordinate geometry to ten O2- atoms. There are a spread of K–O bond distances ranging from 2.75–3.39 Å. Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with two equivalent UO6 octahedra and corners with four equivalent SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.33 Å) and two longer (2.38 Å) Ca–O bond lengths. U6+ is bonded to six O2- atoms to form UO6 octahedra that share corners with two equivalent CaO6 octahedra and corners with four equivalent SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (1.88 Å) and four longer (2.23 Å) U–O bond lengths. Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one CaO6 octahedra, a cornercorner with one UO6 octahedra, and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 21–28°. There are a spread of Si–O bond distances ranging from 1.59–1.67 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to three K1+, one U6+, and one Si4+ atom. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two equivalent K1+ and two equivalent Si4+ atoms. In the third O2- site, O2- is bonded in a linear geometry to three K1+ and two equivalent Si4+ atoms. In the fourth O2- site, O2- is bonded in a distorted linear geometry to two equivalent K1+, one Ca2+, and one U6+ atom. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to two K1+, one Ca2+, and one Si4+ atom.