Open shells in reduced-density-matrix-functional theory

Physical Review A 72, 30501 (2005)

Open shells in reduced-density-matrix-functional theory

N.N. Lathiotakis, N. Helbig, E.K.U. Gross

Reduced-density-matrix-functional theory is applied to open-shell systems. We introduce a spin-restricted formulation by appropriately expressing approximate correlation-energy functionals in terms of spin-dependent occupation numbers and spin-independent natural orbitals. We demonstrate that the additional constraint of total-spin conservation is indispensable for the proper treatment of open-shell systems. The formalism is applied to the first-row open-shell atoms. The obtained ground-state energies are in very good agreement with the exact values as well as other state of the art quantum chemistry calculations.

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