Covalency Effects in KMnF3

The covalency parameters between manganese 3 d orbitals and the neigh-boring fluorine 2 s , 2 p orbitals in KMnF 3 are calculated by means of the molecular orbital method. Particular attention is paid to the interrelation of the MO method with several other methods. The calculated values of the fractions of unpaired spins in a fluorine ion are f s =0.0043 and f σ - f π =0.0057. The cubic field splitting 10 D q of manganese 3 d orbitals is evaluated at 3240 cm -1 . The quantitative agreement with experiments is unsatisfactory. It is emphasized that taking account of the Coulomb correlation effect is important to improve the theory.