Role of the electrostatic model in calculating rare-earth crystal-field parameters

The Sternheimer method is used to derive shielding parameters and antishielding factors for the whale series of rare earths using relativistic wavefunctions. It is found that the shielding parameter sigma(2) of the 4f electronic shell is decreased compared to earlier calculations. The sigma(4) and sigma(6) parameters are calculated for the first time for all rare-earth ions. In all cases, they are found to be small. The influence of the various calculated parameters on the crystal-field parameters for the cases Nd:LiYF4 and Pr:LiYF4 is studied. Present corrections result in ab initio crystal-field parameters that are in excellent agreement with experimentally fitted phenomenological parameters. The nuclear antishielding factors gamma(infinity) are found to essentially agree with earlier findings. These are also found to agree with some early experiments. The various wavefunctions used are derived from a relativistic Desclaux code. These are mon external compared to standard Hartree-Fock wavefunctions. (C) 1998 Elsevier Science S.A.