DOE OSTI2020
Tm3FeSi3 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are three inequivalent Tm3+ sites. In the first Tm3+ site, Tm3+ is bonded to six Si4- atoms to form distorted TmSi6 pentagonal pyramids that share corners with four equivalent TmSi6 pentagonal pyramids, corners with two equivalent FeSi4 tetrahedra, edges with two equivalent TmSi6 pentagonal pyramids, and edges with two equivalent FeSi4 tetrahedra. There are a spread of Tm–Si bond distances ranging from 2.82–3.11 Å. In the second Tm3+ site, Tm3+ is bonded in a 7-coordinate geometry to seven Si4- atoms. There are a spread of Tm–Si bond distances ranging from 2.85–3.23 Å. In the third Tm3+ site, Tm3+ is bonded in a 7-coordinate geometry to seven Si4- atoms. There are a spread of Tm–Si bond distances ranging from 2.90–3.06 Å. Fe3+ is bonded to four Si4- atoms to form FeSi4 tetrahedra that share corners with two equivalent TmSi6 pentagonal pyramids, corners with two equivalent FeSi4 tetrahedra, edges with two equivalent TmSi6 pentagonal pyramids, and edges with two equivalent FeSi4 tetrahedra. There are a spread of Fe–Si bond distances ranging from 2.32–2.45 Å. There are three inequivalent Si4- sites. In the first Si4- site, Si4- is bonded in a 10-coordinate geometry to six Tm3+, three equivalent Fe3+, and one Si4- atom. The Si–Si bond length is 2.76 Å. In the second Si4- site, Si4- is bonded in a 9-coordinate geometry to seven Tm3+ and two Si4- atoms. There are one shorter (2.50 Å) and one longer (2.52 Å) Si–Si bond lengths. In the third Si4- site, Si4- is bonded in a 9-coordinate geometry to seven Tm3+, one Fe3+, and one Si4- atom.