Materials Data on CaMg6C by Materials Project
CaMg6C crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. Ca is bonded in a 2-coordinate geometry to six Mg atoms. There are two shorter (3.18 Å) and four longer (3.77 Å) Ca–Mg bond lengths. There are four inequivalent Mg sites. In the first Mg site, Mg is bonded in an L-shaped geometry to two equivalent Mg and two equivalent C atoms. Both Mg–Mg bond lengths are 3.15 Å. Both Mg–C bond lengths are 2.26 Å. In the second Mg site, Mg is bonded in a 2-coordinate geometry to two equivalent Ca and eight Mg atoms. There are a spread of Mg–Mg bond distances ranging from 3.03–3.31 Å. In the third Mg site, Mg is bonded in a single-bond geometry to two equivalent Mg and one C atom. The Mg–C bond length is 2.32 Å. In the fourth Mg site, Mg is bonded to four equivalent Ca and eight Mg atoms to form MgCa4Mg8 cuboctahedra that share corners with six equivalent MgCa4Mg8 cuboctahedra, corners with four equivalent CMg6 pentagonal pyramids, edges with two equivalent MgCa4Mg8 cuboctahedra, edges with two equivalent CMg6 pentagonal pyramids, and faces with two equivalent MgCa4Mg8 cuboctahedra. Both Mg–Mg bond lengths are 3.31 Å. C is bonded to six Mg atoms to form distorted CMg6 pentagonal pyramids that share corners with four equivalent MgCa4Mg8 cuboctahedra, edges with two equivalent MgCa4Mg8 cuboctahedra, and edges with two equivalent CMg6 pentagonal pyramids.