Theoretical calculations of effective exchange integrals by spin projected and unprojected broken-symmetry methods II: Cluster models of Jahn-Teller distorted K2CuF4 solid

In the strong correlated perovskite-type copper fluoride of K2CuF4, the degree of freedom in d orbitals of copper cation should be considered to understand the magnetism. We performed the cluster model calculations under consideration of octahedral fluorine anions around copper cation, in order to investigate the magnetism. At the amplitude of Jahn-Teller distortion, the alternate d(z2-x2) type orbital ordering and the experimental effective exchange integral (J(ab)) value were reproduced. The calculated potential energy curves were discussed, from the viewpoint of the theoretical total energy in the Jahn-Teller distorted structure proposed by Kanamori. (C) 2008 Elsevier Ltd. All rights reserved.