Ab initio lanthanide crystal field calculation for small internuclear separations

Abstract

Pr3+-Cl- intrinsic crystal field parameters Ak have been calculated for three internuclear separations, between the equilibrium distance (R0=5.5812 au) in PrCl3 and 4.0812 au. The results show that pi -bonding and charge penetration contributions both tend to increase the A4/A6 ratio for interionic separations much smaller than the equilibrium spacing. It follows that mechanisms similar to those which have been successfully employed for crystal field calculations in ionic solids may also be invoked to explain the observed crystal fields in covalently bonded solids, where this ratio is much larger, and metals, where it is negative.