DOE OSTI2020
Mg14NiGa crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. there are seven inequivalent Mg sites. In the first Mg site, Mg is bonded to twelve Mg atoms to form MgMg12 cuboctahedra that share corners with four equivalent GaMg10Ni2 cuboctahedra, corners with fourteen MgMg12 cuboctahedra, edges with six MgMg12 cuboctahedra, faces with two equivalent NiMg10Ga2 cuboctahedra, and faces with twelve MgMg12 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.10–3.19 Å. In the second Mg site, Mg is bonded to twelve Mg atoms to form MgMg12 cuboctahedra that share corners with four equivalent NiMg10Ga2 cuboctahedra, corners with fourteen MgMg12 cuboctahedra, edges with ten MgMg12 cuboctahedra, faces with two equivalent GaMg10Ni2 cuboctahedra, and faces with eight MgMg12 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.07–3.22 Å. In the third Mg site, Mg is bonded to eight Mg, two equivalent Ni, and two equivalent Ga atoms to form distorted MgMg8Ga2Ni2 cuboctahedra that share corners with eighteen MgMg12 cuboctahedra, edges with two equivalent NiMg10Ga2 cuboctahedra, edges with two equivalent GaMg10Ni2 cuboctahedra, edges with six MgMg8Ga2Ni2 cuboctahedra, faces with two equivalent NiMg10Ga2 cuboctahedra, faces with two equivalent GaMg10Ni2 cuboctahedra, and faces with six MgMg8Ga2Ni2 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 2.97–3.14 Å. There are one shorter (3.05 Å) and one longer (3.17 Å) Mg–Ni bond lengths. There are one shorter (3.02 Å) and one longer (3.20 Å) Mg–Ga bond lengths. In the fourth Mg site, Mg is bonded to twelve Mg atoms to form MgMg12 cuboctahedra that share corners with four equivalent NiMg10Ga2 cuboctahedra, corners with four equivalent GaMg10Ni2 cuboctahedra, corners with ten MgMg8Ga2Ni2 cuboctahedra, edges with ten MgMg12 cuboctahedra, and faces with ten MgMg12 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.09–3.24 Å. In the fifth Mg site, Mg is bonded in a 12-coordinate geometry to six Mg, one Ni, and one Ga atom. There are one shorter (3.07 Å) and one longer (3.16 Å) Mg–Mg bond lengths. The Mg–Ni bond length is 2.89 Å. The Mg–Ga bond length is 2.93 Å. In the sixth Mg site, Mg is bonded in a distorted single-bond geometry to seven Mg and one Ni atom. Both Mg–Mg bond lengths are 3.13 Å. The Mg–Ni bond length is 2.93 Å. In the seventh Mg site, Mg is bonded to eleven Mg and one Ga atom to form distorted MgMg11Ga cuboctahedra that share corners with six equivalent MgMg11Ga cuboctahedra, edges with two equivalent GaMg10Ni2 cuboctahedra, edges with ten MgMg12 cuboctahedra, a faceface with one GaMg10Ni2 cuboctahedra, faces with three equivalent NiMg10Ga2 cuboctahedra, and faces with ten MgMg12 cuboctahedra. The Mg–Ga bond length is 3.01 Å. Ni is bonded to ten Mg and two equivalent Ga atoms to form distorted NiMg10Ga2 cuboctahedra that share corners with six equivalent NiMg10Ga2 cuboctahedra, corners with twelve MgMg12 cuboctahedra, edges with two equivalent GaMg10Ni2 cuboctahedra, edges with four equivalent MgMg8Ga2Ni2 cuboctahedra, faces with two equivalent GaMg10Ni2 cuboctahedra, and faces with twelve MgMg12 cuboctahedra. Both Ni–Ga bond lengths are 3.13 Å. Ga is bonded to ten Mg and two equivalent Ni atoms to form distorted GaMg10Ni2 cuboctahedra that share corners with six equivalent GaMg10Ni2 cuboctahedra, corners with twelve MgMg12 cuboctahedra, edges with two equivalent NiMg10Ga2 cuboctahedra, edges with eight MgMg8Ga2Ni2 cuboctahedra, faces with two equivalent NiMg10Ga2 cuboctahedra, and faces with eight MgMg12 cuboctahedra.