Preparation, magnetic properties and structure of beta-Li3CrF6

The beta-modification of Li3CrF6 was prepared by heating an appropriate mixture of LiF and CrF3 at 820 degrees C in an argon-filled quartz glass ampoule with subsequent slow cooling to room temperature. beta-Li3CrF6 is isotypic to beta-Li3VF6 and crystallizes in space group C2/c with a = 14.381(1), b = 8.605(1), c = 10.012(1) Angstrom, beta = 94.85(1)degrees. The structural parameters were refined using single crystal data. A comparison of its structure with that of other beta-Li3MF6 (M = Ti, Ga, and Al) compounds is made for the analysis of a static Jahn-Teller effect within quasi-isolated [TiF6](3-) octahedra. Emphasis is given to the geometry and coordination number of various LiFn polyhedra. The magnetic moment of the title compound was close to that of a free-ion value. Calculations of the Madelung part of the lattice energy (MAPLE) were performed to ascertain the accuracy of the positional parameters of various atoms in the structure. (C) 2000 Elsevier Science Ltd. All rights reserved.