Pressure dependence of magnetic coupling in ionic solids from abinitio cluster model calculations

The dependence of the magnetic coupling constant, J, with the pressure has been studied by an ab initio cluster model approach in a typical ionic solid such as KNiF3. By computing J at different values of the lattice parameter R, we predict a power law of the form ‖J‖≊R−n with 10.5<n<13.3 in good agreement with the suggested experimental value. This behavior is found even for the simplest Ni2F cluster model described by a complete active space configuration interaction wave function in which the active orbitals correspond to the open shell of each Ni2+ cation.