DOE OSTI2020
Ba3SrSn12 crystallizes in the orthorhombic Pmm2 space group. The structure is three-dimensional. there are three inequivalent Ba sites. In the first Ba site, Ba is bonded to twelve Sn atoms to form distorted BaSn12 cuboctahedra that share corners with two equivalent BaSn12 cuboctahedra, corners with four equivalent SrSn12 cuboctahedra, and faces with eight BaSn12 cuboctahedra. There are a spread of Ba–Sn bond distances ranging from 3.63–3.76 Å. In the second Ba site, Ba is bonded to twelve Sn atoms to form distorted BaSn12 cuboctahedra that share corners with six BaSn12 cuboctahedra, faces with four BaSn12 cuboctahedra, and faces with four equivalent SrSn12 cuboctahedra. There are a spread of Ba–Sn bond distances ranging from 3.62–3.74 Å. In the third Ba site, Ba is bonded to twelve Sn atoms to form distorted BaSn12 cuboctahedra that share corners with six BaSn12 cuboctahedra, faces with two equivalent SrSn12 cuboctahedra, and faces with six BaSn12 cuboctahedra. There are a spread of Ba–Sn bond distances ranging from 3.62–3.76 Å. Sr is bonded to twelve Sn atoms to form distorted SrSn12 cuboctahedra that share corners with two equivalent SrSn12 cuboctahedra, corners with four equivalent BaSn12 cuboctahedra, faces with two equivalent SrSn12 cuboctahedra, and faces with six BaSn12 cuboctahedra. There are a spread of Sr–Sn bond distances ranging from 3.59–3.73 Å. There are eight inequivalent Sn sites. In the first Sn site, Sn is bonded in a 4-coordinate geometry to two equivalent Ba, two equivalent Sr, and six Sn atoms. There are two shorter (3.21 Å) and four longer (3.24 Å) Sn–Sn bond lengths. In the second Sn site, Sn is bonded in a 4-coordinate geometry to four Ba and six Sn atoms. There are two shorter (3.20 Å) and four longer (3.24 Å) Sn–Sn bond lengths. In the third Sn site, Sn is bonded in a 4-coordinate geometry to two Ba, two equivalent Sr, and six Sn atoms. There are one shorter (3.21 Å) and four longer (3.25 Å) Sn–Sn bond lengths. In the fourth Sn site, Sn is bonded in a 10-coordinate geometry to four Ba and six Sn atoms. There are a spread of Sn–Sn bond distances ranging from 3.12–3.25 Å. In the fifth Sn site, Sn is bonded in a 4-coordinate geometry to two equivalent Ba, two equivalent Sr, and six Sn atoms. Both Sn–Sn bond lengths are 3.18 Å. In the sixth Sn site, Sn is bonded in a 4-coordinate geometry to four Ba and six Sn atoms. Both Sn–Sn bond lengths are 3.19 Å. In the seventh Sn site, Sn is bonded in a 10-coordinate geometry to three Ba, one Sr, and six Sn atoms. The Sn–Sn bond length is 3.12 Å. In the eighth Sn site, Sn is bonded in a 10-coordinate geometry to three Ba, one Sr, and six Sn atoms. The Sn–Sn bond length is 3.15 Å.