Spin multiconfigurational study

C. Clavaguera-Sarro, V. Vallet, D. Maynau, and C. J. Marsden, Can density functional methods be used for open-sheh actinide molecules Comparison with multiconfigurational spin-orbit studies, J. Chem. Phys. 121, 5312 (2004). 

Variational optimization of equation (11.9), where we are concerned with only one projection of tp corresponding to a particular electronic eigenstate, has been extensively studied. There are at least two well-developed techniques for such situations, namely, the multiconfiguration SCF (MCSCF) and iterative natural spin-orbital (INSO) approaches. 

We have presented results from a theoretical study of the electronic and molecular properties of the PbO molecule. A multiconfigurational approach has been used, which essentially works with non-relativistic wave functions. Relativity is introduced in two steps. First scalar relativistic elfects are included through the use of the Douglas-Kroll Hamiltonian and a correspondingly constructed AO basis set. Spin-orbit effects are included by allowing different CASSCF wave functions to mix under the influence of a spin-orbit Hamiltonian. 

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