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.