DOE OSTI2020
MgSn2 crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. there are two inequivalent Mg sites. In the first Mg site, Mg is bonded to four Mg and eight Sn atoms to form distorted MgMg4Sn8 cuboctahedra that share corners with ten SnMg6 cuboctahedra, corners with twelve MgMg4Sn8 cuboctahedra, edges with three equivalent MgMg4Sn8 cuboctahedra, edges with seven SnMg6 cuboctahedra, faces with two equivalent SnMg4Sn8 cuboctahedra, and faces with six MgMg4Sn8 cuboctahedra. There are two shorter (3.34 Å) and two longer (3.39 Å) Mg–Mg bond lengths. There are six shorter (3.25 Å) and two longer (3.40 Å) Mg–Sn bond lengths. In the second Mg site, Mg is bonded to four Mg and eight Sn atoms to form distorted MgMg4Sn8 cuboctahedra that share corners with six equivalent SnMg4Sn8 cuboctahedra, corners with twelve MgMg4Sn8 cuboctahedra, edges with three equivalent MgMg4Sn8 cuboctahedra, edges with nine SnMg6 cuboctahedra, faces with two equivalent SnMg4Sn8 cuboctahedra, and faces with six MgMg4Sn8 cuboctahedra. Both Mg–Mg bond lengths are 3.34 Å. There are a spread of Mg–Sn bond distances ranging from 3.23–3.41 Å. There are four inequivalent Sn sites. In the first Sn site, Sn is bonded in a distorted water-like geometry to two equivalent Mg and four equivalent Sn atoms. All Sn–Sn bond lengths are 3.26 Å. In the second Sn site, Sn is bonded in a 12-coordinate geometry to four equivalent Mg and two equivalent Sn atoms. Both Sn–Sn bond lengths are 3.31 Å. In the third Sn site, Sn is bonded to six Mg atoms to form distorted SnMg6 cuboctahedra that share corners with four equivalent MgMg4Sn8 cuboctahedra, corners with twelve SnMg6 cuboctahedra, edges with four SnMg6 cuboctahedra, edges with ten MgMg4Sn8 cuboctahedra, and faces with two equivalent SnMg6 cuboctahedra. In the fourth Sn site, Sn is bonded to four Mg and eight Sn atoms to form distorted SnMg4Sn8 cuboctahedra that share corners with twelve MgMg4Sn8 cuboctahedra, corners with fourteen SnMg6 cuboctahedra, edges with two equivalent SnMg6 cuboctahedra, edges with six MgMg4Sn8 cuboctahedra, faces with four MgMg4Sn8 cuboctahedra, and faces with four equivalent SnMg4Sn8 cuboctahedra. Both Sn–Sn bond lengths are 3.34 Å.