Dipotassium heptafluorotantalate(V), β-K2TaF7, at 509 K
Journal article, 2006
Upon heating to 509 K, monoclinic α-K2TaF7 (P21/c) transforms to orthorhombic β-K2TaF7 (Pnma) which is composed of discrete K+ cations and TaF72- anions. In the anion, the Ta atom is sevenfold coordinated by F atoms, with the Ta-F distance varying from 1.88(2) to 1.965(19) Å. The two independent K+ cations are surrounded by F atoms positioned within 2.740(17)-2.979(10) and 2.989(17)-3.15(5) Å. Ta, both K and one of the four F atoms are located on a mirror plane, Wyckoff position 4c.