A new theory, called Multiconfigurational Pair Density Functional Theory, MC-PDFT, is presented, which combines multiconfigurational wavefunctions with density functional theory. A multiconfigurational reference wavefunction with correct spin and space symmetry, of multiconfigurational SCF type, MCSCF, is used to compute the total electronic density, the pair density and their gradients, and the kinetic and Coulomb contributions to the total electronic energy. Local spin-densities and their gradients are derived from the spinless densities and used with existing Kohn-Sham spin-density functionals to compute the exchange and correlation contribution to the electronic energy. Double-counting of dynamic correlation is mainly avoided because no MCSCF correlation energy contribution is added to the total energy. Spectroscopic properties of various diatomics including CaO, NiCl and Cr2 were  computed, together with some atomic and molecular excitation energies. The method has a computational cost similar to multiconfigurational SCF, but a quantitative accuracy comparable or superior to multireference perturbation theory methods.

Multiconfigurational pair density functional theory

248th National Meeting (2014)

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