Projection-based DMRG-in-DFT embedding corrected by non-additive exchange-correlation

TL;DR

This paper enhances projection-based DMRG-in-DFT embedding by incorporating exact exchange and a multireference adiabatic connection scheme to improve accuracy in strongly correlated systems.

Contribution

It introduces a correction method combining exact exchange and multireference AC to address nonadditive exchange-correlation errors in DMRG-in-DFT embedding.

Findings

Improved accuracy in H2O chain dissociation

Enhanced description of CN bond cleavage in propionitrile

Reduction of nonadditive exchange-correlation errors

Abstract

The projection-based wave function (WF)-in-DFT embedding enables an efficient description of both the energetics and properties of large and complex chemical systems, with accuracy exceeding that of pure DFT. Recently, we have proposed using the density matrix renormalization group (DMRG) as the WF method for molecules containing strongly correlated fragments [Beran, P. et al. J. Phys. Chem. Lett. 2023, 14, 3, 716-722]. In this work, we demonstrate that the accuracy of the DMRG-in-DFT approach is primarily limited by the approximate treatment of the coupling between the active component and its environment through nonadditive exchange-correlation functionals. To address this issue, we combine exact exchange to reduce the nonadditive exchange error with a multireference adiabatic connection (AC) scheme to recover nonadditive correlation. The performance of the improved DMRG-in-DFT embedding is illustrated on two prototypical strongly correlated systems: the dissociation of the H20 chain and the cleavage of a triple CN bond in propionitrile.