DOE OSTI2020
Mg6YCu crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. there are four inequivalent Mg sites. In the first Mg site, Mg is bonded in a 12-coordinate geometry to eight Mg, two equivalent Y, and two equivalent Cu atoms. There are a spread of Mg–Mg bond distances ranging from 3.03–3.35 Å. There are one shorter (3.13 Å) and one longer (3.34 Å) Mg–Y bond lengths. Both Mg–Cu bond lengths are 3.09 Å. In the second Mg site, Mg is bonded to ten Mg and two equivalent Y atoms to form MgY2Mg10 cuboctahedra that share corners with four equivalent YMg10Cu2 cuboctahedra, corners with six equivalent MgY2Mg10 cuboctahedra, edges with two equivalent YMg10Cu2 cuboctahedra, edges with twelve MgY2Mg8Cu2 cuboctahedra, faces with two equivalent YMg10Cu2 cuboctahedra, faces with six equivalent CuY2Mg10 cuboctahedra, and faces with eight MgY2Mg10 cuboctahedra. There are four shorter (3.08 Å) and two longer (3.12 Å) Mg–Mg bond lengths. Both Mg–Y bond lengths are 3.19 Å. In the third Mg site, Mg is bonded to eight Mg, two equivalent Y, and two equivalent Cu atoms to form distorted MgY2Mg8Cu2 cuboctahedra that share corners with four equivalent CuY2Mg10 cuboctahedra, corners with fourteen MgY2Mg8Cu2 cuboctahedra, edges with two equivalent CuY2Mg10 cuboctahedra, edges with four equivalent YMg10Cu2 cuboctahedra, edges with eight MgY2Mg10 cuboctahedra, faces with two equivalent YMg10Cu2 cuboctahedra, faces with two equivalent CuY2Mg10 cuboctahedra, and faces with eight MgY2Mg10 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.08–3.30 Å. Both Mg–Y bond lengths are 3.20 Å. There are one shorter (3.15 Å) and one longer (3.32 Å) Mg–Cu bond lengths. In the fourth Mg site, Mg is bonded to ten Mg and two equivalent Cu atoms to form distorted MgMg10Cu2 cuboctahedra that share corners with four equivalent CuY2Mg10 cuboctahedra, corners with fourteen MgY2Mg8Cu2 cuboctahedra, edges with two equivalent CuY2Mg10 cuboctahedra, edges with eight MgY2Mg10 cuboctahedra, faces with two equivalent CuY2Mg10 cuboctahedra, faces with six equivalent YMg10Cu2 cuboctahedra, and faces with eight MgY2Mg10 cuboctahedra. Both Mg–Cu bond lengths are 3.19 Å. Y is bonded to ten Mg and two equivalent Cu atoms to form distorted YMg10Cu2 cuboctahedra that share corners with four equivalent MgY2Mg10 cuboctahedra, corners with six equivalent YMg10Cu2 cuboctahedra, edges with four equivalent CuY2Mg10 cuboctahedra, edges with ten MgY2Mg10 cuboctahedra, faces with two equivalent YMg10Cu2 cuboctahedra, faces with two equivalent CuY2Mg10 cuboctahedra, and faces with twelve MgY2Mg10 cuboctahedra. Both Y–Cu bond lengths are 3.02 Å. Cu is bonded to ten Mg and two equivalent Y atoms to form CuY2Mg10 cuboctahedra that share corners with six equivalent CuY2Mg10 cuboctahedra, corners with twelve MgY2Mg8Cu2 cuboctahedra, edges with four equivalent YMg10Cu2 cuboctahedra, edges with six MgY2Mg8Cu2 cuboctahedra, faces with two equivalent YMg10Cu2 cuboctahedra, faces with two equivalent CuY2Mg10 cuboctahedra, and faces with twelve MgY2Mg10 cuboctahedra.