Model potential calculations for second-row transition metal molecules within the local-spin-density method.

The model potential (MP) method originally proposed by Huzinaga and Bonifacic is extended to spin-polarized local-spin-density calculations, including scalar relativistic effects. The theoretical justification of the MP method in this case is studied and the method of optimization of the basis functions and MP parameters is given. The validity of the frozen core approximation is studied for Mo2, Ru2, and Ag2. It is found that the MP can very accurately reproduce all-electron (AE) results if the 4p electrons of Ag and the 3d electrons of Mo are also considered as valence electrons, although inclusion of these electrons in the core still yields a useful level of accuracy. It is shown that the present MP results are not sensitive to basis set superposition errors (BSSE). Upon inclusion of the scalar relativistic effects the calculated bond length and vibrational frequency of Ag2 are in near perfect agreement with experiment, while the dissociation energy is overestimated by 23% with the ‘‘best’’ local potential (VWN). MP calculations have also been performed for AgH, AgO, and AgF. The same level of agreement with experiment as for Ag2 was found, with the exception of the bond length for AgO. Our calculated bond length is 0.05 Å shorter than the presently accepted experimental value. Since some uncertainty is associated with the spectroscopic assignments for AgO we believe an experimental reexamination would be in order. [ABSTRACT FROM AUTHOR]