DOE OSTI2020
Sm4Ni7Si9 crystallizes in the monoclinic C2 space group. The structure is three-dimensional. there are two inequivalent Sm2+ sites. In the first Sm2+ site, Sm2+ is bonded in a 9-coordinate geometry to nine Si+2.22- atoms. There are a spread of Sm–Si bond distances ranging from 2.92–3.11 Å. In the second Sm2+ site, Sm2+ is bonded in a 9-coordinate geometry to nine Si+2.22- atoms. There are a spread of Sm–Si bond distances ranging from 2.99–3.15 Å. There are five inequivalent Ni+1.71+ sites. In the first Ni+1.71+ site, Ni+1.71+ is bonded in a distorted water-like geometry to four Si+2.22- atoms. There are two shorter (2.30 Å) and two longer (2.83 Å) Ni–Si bond lengths. In the second Ni+1.71+ site, Ni+1.71+ is bonded to four Si+2.22- atoms to form a mixture of distorted corner and edge-sharing NiSi4 tetrahedra. There are a spread of Ni–Si bond distances ranging from 2.28–2.33 Å. In the third Ni+1.71+ site, Ni+1.71+ is bonded in a 5-coordinate geometry to five Si+2.22- atoms. There are a spread of Ni–Si bond distances ranging from 2.32–2.36 Å. In the fourth Ni+1.71+ site, Ni+1.71+ is bonded in a 6-coordinate geometry to six Si+2.22- atoms. There are a spread of Ni–Si bond distances ranging from 2.34–2.73 Å. In the fifth Ni+1.71+ site, Ni+1.71+ is bonded in a 5-coordinate geometry to five Si+2.22- atoms. There are a spread of Ni–Si bond distances ranging from 2.32–2.52 Å. There are seven inequivalent Si+2.22- sites. In the first Si+2.22- site, Si+2.22- is bonded in a 9-coordinate geometry to four Sm2+, three Ni+1.71+, and two Si+2.22- atoms. Both Si–Si bond lengths are 2.49 Å. In the second Si+2.22- site, Si+2.22- is bonded in a 9-coordinate geometry to four Sm2+, four Ni+1.71+, and one Si+2.22- atom. The Si–Si bond length is 2.45 Å. In the third Si+2.22- site, Si+2.22- is bonded in a 8-coordinate geometry to four Sm2+ and four Ni+1.71+ atoms. In the fourth Si+2.22- site, Si+2.22- is bonded in a 8-coordinate geometry to four Sm2+ and four Ni+1.71+ atoms. In the fifth Si+2.22- site, Si+2.22- is bonded in a 2-coordinate geometry to four Sm2+, three Ni+1.71+, and two equivalent Si+2.22- atoms. In the sixth Si+2.22- site, Si+2.22- is bonded in a 2-coordinate geometry to four Sm2+, three Ni+1.71+, and two equivalent Si+2.22- atoms. In the seventh Si+2.22- site, Si+2.22- is bonded in a 11-coordinate geometry to four Sm2+, five Ni+1.71+, and two equivalent Si+2.22- atoms.