First-principles calculation of crystal-field parameters in Nd2Fe14B

A new approach to calculating the crystal-field parameters in a perfect crystal based on real-space charge distribution from energy-band calculations is formulated. The contribution from the charges in the vicinity of the ion is evaluated numerically using a method of successive least-squares fitting. The contribution from other ion sites is approximated by a point-charge model, but with effective ionic charges obtained from the band calculation. The method is applied to the Nd2Fe14B permanent magnet. The crystal-field parameters up to sixth order are calculated for the Nd site. The results are in good agreement with experimental analysis and are qualitatively different from the existing theoretical values based purely on a point-charge model