COMPUTATIONAL ANALYSIS OF CRYSTAL-FIELD PARAMETERS OF RARE-EARTH TRANSITION-METAL COMPOUNDS

The charge distribution of rare-earth transition-metal (RE-TM) compounds is calculated in the local-spin-density approximation (LSDA) and used to analyze the various contributions to crystal field (CF) parameters for the 4f states at the RE site. The LSDA calculations are found to yield the correct sign for all CF parameters but to overestimate the magnitude of the most essential second-order parameter A2(0). It is shown that the charge distribution up to a distance of 100 a.u. from the RE atom has to be taken into consideration for calculating A2(0) and that neither a restriction on the lattice terms (as e.g. in a point charge calculation) nor an exclusion of these contributions is justified a priori. Furthermore, the value of A2(0) is extremely sensitive to changes in occupation among the Re 5d orbitals.