Materials Data on TmFeGe2O7 by Materials Project
TmFeGe2O7 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Tm3+ is bonded to six O2- atoms to form distorted TmO6 pentagonal pyramids that share corners with two equivalent GeO4 tetrahedra, edges with two equivalent FeO6 octahedra, and an edgeedge with one TmO6 pentagonal pyramid. There are a spread of Tm–O bond distances ranging from 2.19–2.38 Å. Fe3+ is bonded to six O2- atoms to form distorted FeO6 octahedra that share corners with four equivalent GeO4 tetrahedra, an edgeedge with one FeO6 octahedra, and edges with two equivalent TmO6 pentagonal pyramids. There are a spread of Fe–O bond distances ranging from 1.99–2.19 Å. There are two inequivalent Ge4+ sites. In the first Ge4+ site, Ge4+ is bonded to four O2- atoms to form GeO4 tetrahedra that share corners with four equivalent FeO6 octahedra and corners with two equivalent TmO6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 45–55°. There are a spread of Ge–O bond distances ranging from 1.77–1.80 Å. In the second Ge4+ site, Ge4+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Ge–O bond distances ranging from 1.75–2.27 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one Tm3+, one Fe3+, and one Ge4+ atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Fe3+ and two Ge4+ atoms. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Tm3+ and one Ge4+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to one Tm3+, one Fe3+, and one Ge4+ atom. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to two Ge4+ atoms.