Coupled cluster method with single and double excitations tailored by matrix product state wave functions

TL;DR

This paper introduces a novel post-DMRG method combining density matrix renormalization group and coupled cluster theories to accurately account for dynamic correlation in strongly correlated molecular systems, demonstrated on complex molecules.

Contribution

The paper presents a new tailored coupled cluster approach that integrates DMRG for non-dynamic correlation with CC for dynamic correlation, enabling accurate post-DMRG calculations.

Findings

Successfully applied to N₂, Cr₂, and oxo-Mn(Salen) molecules.

First post-DMRG computations for oxo-Mn(Salen) energy states.

Provides insights into the energy ordering of low-lying spin states.

Abstract

In the last decade, the quantum chemical version of the density matrix renormalization group (DMRG) method has established itself as the method of choice for calculations of strongly correlated molecular systems. Despite its favourable scaling, it is in practice not suitable for computations of dynamic correlation. We present a novel method for accurate "post-DMRG" treatment of dynamic correlation based on the tailored coupled cluster (CC) theory in which the DMRG method is responsible for the proper description of non-dynamic correlation, whereas dynamic correlation is incorporated through the framework of the CC theory. We illustrate the potential of this method on prominent multireference systems, in particular N$_2$, Cr$_2$ molecules and also oxo-Mn(Salen) for which we have performed the first "post-DMRG" computations in order to shed light on the energy ordering of the lowest spin states.