Preparation, magnetic properties and structure of beta-Li3CrF6

The beta-modification of Li3CrF6 was prepared by heating an appropriate mix ture of LiF and CrF3 at 820 degrees C in an argon-filled quartz glass ampou le with subsequent slow cooling to room temperature. beta-Li3CrF6 is isotyp ic 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 structura l parameters were refined using single crystal data. A comparison of its st ructure with that of other beta-Li3MF6 (M = Ti, Ga, and Al) compounds is ma de for the analysis of a static Jahn-Teller effect within quasi-isolated [T iF6](3-) octahedra. Emphasis is given to the geometry and coordination numb er 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 th e lattice energy (MAPLE) were performed to ascertain the accuracy of the po sitional parameters of various atoms in the structure. (C) 2000 Elsevier Sc ience Ltd. All rights reserved.