Range-separated DFT was implemented within selected configuration interaction (sCI).[1] The PBE density functional is used for the short-range correlation, and CIPSI is used for the long-range.

The introduction of DFT for short range correlation has multiple benefits for QMC simulations. First, it reduces significantly the size of the CI expansion by several orders of magnitude. Secondly, it mimics the effect of a short-range correlation factor such as the Jastrow factor used in QMC simulations, leading to a significant improvement of the nodal surfaces, and energy differences.

The implementation was made in the open source program Quantum Package,[2] which is already interfaced with interfaced with several QMC codes.

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[1] doi:10.1063/1.5082638
[2] doi:10.1021/acs.jctc.9b00176