DOE OSTI2020
SrSi crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. there are five inequivalent Sr sites. In the first Sr site, Sr is bonded in a 7-coordinate geometry to seven Si atoms. There are a spread of Sr–Si bond distances ranging from 3.25–3.33 Å. In the second Sr site, Sr is bonded in a 8-coordinate geometry to eight Si atoms. There are four shorter (3.23 Å) and four longer (3.37 Å) Sr–Si bond lengths. In the third Sr site, Sr is bonded to twelve Si atoms to form distorted SrSi12 cuboctahedra that share corners with four equivalent SrSi5 square pyramids and faces with two equivalent SrSi12 cuboctahedra. There are eight shorter (3.37 Å) and four longer (3.53 Å) Sr–Si bond lengths. In the fourth Sr site, Sr is bonded to five Si atoms to form distorted SrSi5 square pyramids that share corners with two equivalent SrSi12 cuboctahedra and edges with two equivalent SrSi5 square pyramids. There are one shorter (3.41 Å) and four longer (3.43 Å) Sr–Si bond lengths. In the fifth Sr site, Sr is bonded in a square co-planar geometry to four equivalent Si atoms. All Sr–Si bond lengths are 3.29 Å. There are three inequivalent Si sites. In the first Si site, Si is bonded in a 9-coordinate geometry to eight Sr and one Si atom. The Si–Si bond length is 2.40 Å. In the second Si site, Si is bonded in a 9-coordinate geometry to six Sr and three Si atoms. There are one shorter (2.42 Å) and one longer (2.46 Å) Si–Si bond lengths. In the third Si site, Si is bonded in a 9-coordinate geometry to seven Sr and two equivalent Si atoms.