Materials Data on KCa4Si8H16O29 by Materials Project
KCa4Si8H16O29 crystallizes in the tetragonal P4/mnc space group. The structure is three-dimensional. K is bonded in a body-centered cubic geometry to eight equivalent O atoms. All K–O bond lengths are 3.10 Å. Ca is bonded to seven O atoms to form distorted CaO7 pentagonal bipyramids that share a cornercorner with one CaO7 pentagonal bipyramid, corners with four equivalent SiO4 tetrahedra, and faces with two equivalent CaO7 pentagonal bipyramids. There are five shorter (2.43 Å) and two longer (2.49 Å) Ca–O bond lengths. Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with two equivalent CaO7 pentagonal bipyramids and corners with three equivalent SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.61–1.65 Å. There are two inequivalent H sites. In the first H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.97 Å. In the second H site, H is bonded in a single-bond geometry to two O atoms. There is one shorter (1.00 Å) and one longer (1.76 Å) H–O bond length. There are five inequivalent O sites. In the first O site, O is bonded in a bent 150 degrees geometry to two equivalent Si atoms. In the second O site, O is bonded in a bent 150 degrees geometry to two equivalent Si atoms. In the third O site, O is bonded in a distorted water-like geometry to one K, one Ca, and two H atoms. In the fourth O site, O is bonded in a 1-coordinate geometry to two equivalent Ca, one Si, and one H atom. In the fifth O site, O is bonded in a square co-planar geometry to four equivalent Ca atoms.