Materials Data on KTmBeF6 by Materials Project
KBeTmF6 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. K1+ is bonded in a 12-coordinate geometry to twelve F1- atoms. There are a spread of K–F bond distances ranging from 2.76–3.25 Å. Be2+ is bonded in a tetrahedral geometry to four F1- atoms. There is one shorter (1.54 Å) and three longer (1.57 Å) Be–F bond length. Tm3+ is bonded in a 8-coordinate geometry to eight F1- atoms. There are a spread of Tm–F bond distances ranging from 2.21–2.39 Å. There are four inequivalent F1- sites. In the first F1- site, F1- is bonded in a 2-coordinate geometry to two equivalent K1+, one Be2+, and one Tm3+ atom. In the second F1- site, F1- is bonded in a distorted single-bond geometry to one K1+, one Be2+, and one Tm3+ atom. In the third F1- site, F1- is bonded to two equivalent K1+ and two equivalent Tm3+ atoms to form a mixture of distorted corner and edge-sharing FK2Tm2 tetrahedra. In the fourth F1- site, F1- is bonded in a distorted single-bond geometry to three equivalent K1+, one Be2+, and one Tm3+ atom.