Materials Data on Sr5Ca3Si4 by Materials Project

Abstract

Sr5Ca3Si4 crystallizes in the monoclinic Pm space group. The structure is three-dimensional. there are five inequivalent Sr2+ sites. In the first Sr2+ site, Sr2+ is bonded to five Si4- atoms to form distorted SrSi5 trigonal bipyramids that share corners with four equivalent SrSi5 square pyramids, corners with three equivalent SrSi4 tetrahedra, corners with five CaSi4 tetrahedra, edges with two equivalent SrSi5 square pyramids, an edgeedge with one SrSi4 tetrahedra, edges with five CaSi4 tetrahedra, and edges with two equivalent SrSi5 trigonal bipyramids. There are a spread of Sr–Si bond distances ranging from 3.23–3.58 Å. In the second Sr2+ site, Sr2+ is bonded to five Si4- atoms to form distorted SrSi5 square pyramids that share corners with three equivalent SrSi4 tetrahedra, corners with five CaSi4 tetrahedra, corners with four equivalent SrSi5 trigonal bipyramids, edges with two equivalent SrSi5 square pyramids, an edgeedge with one SrSi4 tetrahedra, edges with five CaSi4 tetrahedra, and edges with two equivalent SrSi5 trigonal bipyramids. There are a spread of Sr–Si bond distances ranging from 3.27–3.62 Å. In the third Sr2+ site, Sr2+ is bonded in a 5-coordinate geometry to five Si4- atoms. There are a spread of Sr–Si bond distances ranging from 3.24–3.67 Å. In the fourth Sr2+ site, Sr2+ is bonded in a 5-coordinate geometry to five Si4- atoms. There are a spread of Sr–Si bond distances ranging from 3.36–3.68 Å. In the fifth Sr2+ site, Sr2+ is bonded to four Si4- atoms to form SrSi4 tetrahedra that share corners with three equivalent SrSi5 square pyramids, corners with two equivalent SrSi4 tetrahedra, corners with six CaSi4 tetrahedra, corners with three equivalent SrSi5 trigonal bipyramids, an edgeedge with one SrSi5 square pyramid, edges with two equivalent CaSi4 tetrahedra, and an edgeedge with one SrSi5 trigonal bipyramid. There are a spread of Sr–Si bond distances ranging from 3.13–3.20 Å. There are three inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to four Si4- atoms to form CaSi4 tetrahedra that share corners with three equivalent SrSi5 square pyramids, corners with two equivalent SrSi4 tetrahedra, corners with six CaSi4 tetrahedra, corners with three equivalent SrSi5 trigonal bipyramids, an edgeedge with one SrSi5 square pyramid, edges with two equivalent CaSi4 tetrahedra, and an edgeedge with one SrSi5 trigonal bipyramid. There are a spread of Ca–Si bond distances ranging from 3.05–3.12 Å. In the second Ca2+ site, Ca2+ is bonded to four Si4- atoms to form CaSi4 tetrahedra that share corners with two equivalent SrSi5 square pyramids, corners with eight CaSi4 tetrahedra, edges with two equivalent SrSi5 square pyramids, edges with two equivalent SrSi4 tetrahedra, and edges with two equivalent SrSi5 trigonal bipyramids. There are three shorter (3.10 Å) and one longer (3.14 Å) Ca–Si bond lengths. In the third Ca2+ site, Ca2+ is bonded to four Si4- atoms to form CaSi4 tetrahedra that share corners with four equivalent SrSi4 tetrahedra, corners with four CaSi4 tetrahedra, corners with two equivalent SrSi5 trigonal bipyramids, edges with two equivalent SrSi5 square pyramids, edges with two equivalent CaSi4 tetrahedra, and edges with two equivalent SrSi5 trigonal bipyramids. There are a spread of Ca–Si bond distances ranging from 3.02–3.09 Å. There are four inequivalent Si4- sites. In the first Si4- site, Si4- is bonded in a 9-coordinate geometry to six Sr2+ and three Ca2+ atoms. In the second Si4- site, Si4- is bonded in a 9-coordinate geometry to six Sr2+ and three Ca2+ atoms. In the third Si4- site, Si4- is bonded in a 9-coordinate geometry to five Sr2+ and four Ca2+ atoms. In the fourth Si4- site, Si4- is bonded in a 9-coordinate geometry to seven Sr2+ and two Ca2+ atoms.