Spin-orbit interaction pseudopotentials

Other SC RECPs start from different reference data, mostly omitting spin-orbit interactions, but all approaches use, as reference data, the shape of the valence orbitals in the spatial valence region and their corresponding one-particle energies. We omit details concerning energy-adjusted and other types of relativistic pseudopotentials or effective core potentials. At this point, we summarize some characteristics of valence-only methods such as RECPs. 

Once again the quality of the valence correlation treatment is crucial, making the large-core pseudopotential calculation (even without a CPP correction in this case) more accurate than a fiilly relativistic all-electron calculation. Another remark is relative to the comparison of the two pseudopotential SOCI calculations. A DGCI treatment, which in principle is better than a CI/SO one when large spin-orbit interaction is involved, does not guaranty by itself an accurate SOCI calculation, since in this example a CI /SO method gave much more re-... 

The spin-orbit operators for the model potential and pseudopotential approximations are one-electron operators. These operators include the effect of the two-electron spin-orbit interaction used in the mean-field approximation to derive the model potential or pseudopotential. Molecular calculations with these potentials therefore include, at least at the atomic level, the two-electron spin-orbit terms. This is just the kind of approximation we are looking for. 

A. Weigand, X. Cao, V. Vallet, J.-P. Flament, and M. Dolg, Multi-configuration Dirac-Hartree-Fock adjusted energy-consistent pseudopotential for uranium spin-orbit configuration interaction and Fock-space coupled-cluster study of U and J. Phys. Chem. A, 113, 11509-11516(2009). 

Weigand A, Cao X, Vallet V, Flament JP, Dolg M. Multi-configuration Diract-Hartree-Fock Adjusted Energy-consistent Pseudopotential for Uranium Spin-orbit Configuration Interaction and Fock-Space Coupled-Cluster Study of U + and U + J Phys Chem A 2009 1 IJ-llSOO-llSlb. 

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