DOE OSTI2020
Sr4Au7Sn9 crystallizes in the tetragonal P-4m2 space group. The structure is three-dimensional. there are three inequivalent Sr sites. In the first Sr site, Sr is bonded in a 8-coordinate geometry to six Au and ten Sn atoms. There are four shorter (3.66 Å) and two longer (3.83 Å) Sr–Au bond lengths. There are a spread of Sr–Sn bond distances ranging from 3.66–3.83 Å. In the second Sr site, Sr is bonded in a 12-coordinate geometry to eight Au and eight Sn atoms. There are four shorter (3.61 Å) and four longer (3.71 Å) Sr–Au bond lengths. There are a spread of Sr–Sn bond distances ranging from 3.63–3.81 Å. In the third Sr site, Sr is bonded in a 8-coordinate geometry to six Au and ten Sn atoms. There are four shorter (3.66 Å) and two longer (3.83 Å) Sr–Au bond lengths. There are a spread of Sr–Sn bond distances ranging from 3.66–3.83 Å. There are seven inequivalent Au sites. In the first Au site, Au is bonded in a 9-coordinate geometry to four equivalent Sr and five Sn atoms. There are one shorter (2.68 Å) and four longer (2.85 Å) Au–Sn bond lengths. In the second Au site, Au is bonded in a 9-coordinate geometry to four equivalent Sr and five Sn atoms. All Au–Sr bond lengths are 3.71 Å. There are one shorter (2.71 Å) and four longer (2.83 Å) Au–Sn bond lengths. In the third Au site, Au is bonded in a 9-coordinate geometry to four equivalent Sr and five Sn atoms. There are one shorter (2.68 Å) and four longer (2.85 Å) Au–Sn bond lengths. In the fourth Au site, Au is bonded in a 9-coordinate geometry to four equivalent Sr and five Sn atoms. There are one shorter (2.71 Å) and four longer (2.83 Å) Au–Sn bond lengths. In the fifth Au site, Au is bonded in a 4-coordinate geometry to four equivalent Sr and four equivalent Sn atoms. All Au–Sn bond lengths are 2.81 Å. In the sixth Au site, Au is bonded to four Sr and eight Sn atoms to form distorted AuSr4Sn8 tetrahedra that share corners with four equivalent AuSr4Sn8 tetrahedra, corners with twelve SnSr4Au4 tetrahedra, edges with two equivalent SnSr4Au4 tetrahedra, faces with four equivalent SnSr4Sn4Au4 cuboctahedra, and faces with four equivalent AuSr4Sn8 tetrahedra. There are four shorter (2.91 Å) and four longer (3.41 Å) Au–Sn bond lengths. In the seventh Au site, Au is bonded in a 4-coordinate geometry to four equivalent Sr and four equivalent Sn atoms. All Au–Sn bond lengths are 2.81 Å. There are five inequivalent Sn sites. In the first Sn site, Sn is bonded in a 3-coordinate geometry to four equivalent Sr, three Au, and two equivalent Sn atoms. Both Sn–Sn bond lengths are 2.91 Å. In the second Sn site, Sn is bonded in a 9-coordinate geometry to four equivalent Sr and five Au atoms. In the third Sn site, Sn is bonded to four Sr and four Au atoms to form distorted SnSr4Au4 tetrahedra that share corners with two equivalent SnSr4Sn4Au4 cuboctahedra, corners with four equivalent AuSr4Sn8 tetrahedra, an edgeedge with one SnSr4Sn4Au4 cuboctahedra, edges with four equivalent SnSr4Au4 tetrahedra, and faces with four equivalent SnSr4Au4 tetrahedra. In the fourth Sn site, Sn is bonded to four Sr and four Au atoms to form distorted SnSr4Au4 tetrahedra that share corners with four equivalent SnSr4Sn4Au4 cuboctahedra, corners with two equivalent AuSr4Sn8 tetrahedra, an edgeedge with one AuSr4Sn8 tetrahedra, edges with four equivalent SnSr4Au4 tetrahedra, and faces with four equivalent SnSr4Au4 tetrahedra. In the fifth Sn site, Sn is bonded to four Sr, four equivalent Au, and four equivalent Sn atoms to form SnSr4Sn4Au4 cuboctahedra that share corners with four equivalent SnSr4Sn4Au4 cuboctahedra, corners with twelve SnSr4Au4 tetrahedra, edges with two equivalent SnSr4Au4 tetrahedra, faces with four equivalent SnSr4Sn4Au4 cuboctahedra, and faces with four equivalent AuSr4Sn8 tetrahedra.