Materials Data on BaCu9Si4 by Materials Project
BaCu9Si4 crystallizes in the tetragonal I4/mcm space group. The structure is three-dimensional. Ba2+ is bonded in a 8-coordinate geometry to eight equivalent Si4- atoms. All Ba–Si bond lengths are 3.42 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 one shorter (2.48 Å) and two longer (2.50 Å) Cu–Cu bond lengths. There are two shorter (2.54 Å) and two longer (2.58 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 2.57 Å. There are a spread of Cu–Si bond distances ranging from 2.46–2.61 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 2.45 Å. Si4- is bonded to two equivalent Ba2+, nine Cu+1.56+, and one Si4- atom to form a mixture of distorted face and corner-sharing SiBa2Cu9Si cuboctahedra. The Si–Si bond length is 2.70 Å.