DOE OSTI2020
Th2FeSi3 is hexagonal omega structure-derived structured and crystallizes in the orthorhombic Imm2 space group. The structure is three-dimensional. there are two inequivalent Th sites. In the first Th site, Th is bonded to four equivalent Fe and eight Si atoms to form a mixture of face and edge-sharing ThFe4Si8 cuboctahedra. All Th–Fe bond lengths are 3.12 Å. There are a spread of Th–Si bond distances ranging from 3.04–3.17 Å. In the second Th site, Th is bonded to two equivalent Fe and ten Si atoms to form a mixture of face and edge-sharing ThFe2Si10 cuboctahedra. Both Th–Fe bond lengths are 3.05 Å. There are a spread of Th–Si bond distances ranging from 3.13–3.26 Å. Fe is bonded in a 3-coordinate geometry to six Th and three Si atoms. There are one shorter (2.27 Å) and two longer (2.34 Å) Fe–Si bond lengths. There are three inequivalent Si sites. In the first Si site, Si is bonded in a 2-coordinate geometry to six Th, two equivalent Fe, and one Si atom. The Si–Si bond length is 2.41 Å. In the second Si site, Si is bonded in a 1-coordinate geometry to six Th, one Fe, and two equivalent Si atoms. Both Si–Si bond lengths are 2.41 Å. In the third Si site, Si is bonded in a 9-coordinate geometry to six Th and three Si atoms.