Finite Ligand Size and Sternheimer Antiscreening in Lanthanide Ions

Abstract

A finite ligand affects the quadrupole potential at the nucleus of a lanthanide ion in two ways: it produces a positive exchange charge in the region of overlap and it reduces the antiscreening of the point-charge interaction due to charge penetration. We estimate the magnitude of the exchange charge contribution in the system Pr3 + - Cl- using a simple model based on calculating the change in the antiscreening of a point charge as it moves towards the lanthanide ion. A significant contribution is produced, which is not sensitive to the position of the exchange charge, showing that the conventional antiscreening factor )' '" cannot properly represent· the effect of anti screening on the ligand contributions to the nuclear quadrupole potential.