Incorporating dynamic correlation into the variational determination method of the second-order reduced density matrix in the doubly occupied configuration interaction space

Abstract

The variational determination of the second-order reduced density matrices arising from N-electron doubly occupied configuration interaction wave functions has recently been proposed as a method to describe systems possessing static correlation in their ground states. In this work, we propose to combine this approach with the on-top pair density functional theory in order to incorporate dynamic correlations and improve the description of systems possessing both types of electron correlation. The procedure requires ensuring that the second-order reduced density matrix elements satisfy determined N-representability variational conditions, as well as other constraints arising from the doubly-occupied configuration interaction wave function features. An analysis of the results obtained through this method, in studies of strongly correlated many-electron systems, shows the usefulness of our proposals.