Materials Data on SrCu9Si4 by Materials Project
SrCu9Si4 crystallizes in the tetragonal I4/mcm space group. The structure is three-dimensional. Sr2+ is bonded in a 8-coordinate geometry to eight equivalent Si4- atoms. All Sr–Si bond lengths are 3.39 Å. There are three inequivalent Cu+1.56+ sites. In the first Cu+1.56+ site, Cu+1.56+ is bonded in a 7-coordinate geometry to three Cu+1.56+ and four equivalent Si4- atoms. There are two shorter (2.46 Å) and one longer (2.47 Å) Cu–Cu bond lengths. There are two shorter (2.52 Å) and two longer (2.57 Å) Cu–Si bond lengths. In the second Cu+1.56+ site, Cu+1.56+ is bonded in a 4-coordinate geometry to one Cu+1.56+ and four equivalent Si4- atoms. The Cu–Cu bond length is 2.56 Å. There are a spread of Cu–Si bond distances ranging from 2.41–2.60 Å. In the third Cu+1.56+ site, Cu+1.56+ is bonded in a 12-coordinate geometry to eight Cu+1.56+ and four equivalent Si4- atoms. All Cu–Si bond lengths are 2.44 Å. Si4- is bonded to two equivalent Sr2+, nine Cu+1.56+, and one Si4- atom to form a mixture of distorted corner and face-sharing SiSr2Cu9Si cuboctahedra. The Si–Si bond length is 2.70 Å.