Multi-reference perturbation theory with Cholesky decomposition for the density matrix renormalization group

TL;DR

This paper introduces a new second-order perturbation theory method based on DMRG and Cholesky decomposition, enabling efficient and accurate treatment of large molecular systems' static and dynamic correlation effects.

Contribution

It develops a novel CD-DMRG-NEVPT2 approach that combines DMRG with Cholesky decomposition for improved multireference perturbation calculations.

Findings

Accurately predicts spin-state energetics of complex molecules.

Demonstrates applicability to systems with over 1000 basis functions.

Resolves a controversy regarding the spin ground state of a cobalt complex.

Abstract

We present a second-order N-electron valence state perturbation theory (NEVPT2) based on a density matrix renormalization group (DMRG) reference wave function that exploits a Cholesky decomposition of the two-electron repulsion integrals (CD-DMRG-NEVPT2). With a parameter-free multireference perturbation theory approach at hand, the latter allows us to efficiently describe static and dynamic correlation in large molecular systems. We demonstrate the applicability of CD-DMRG-NEVPT2 for spin-state energetics of spin-crossover complexes involving calculations with more than 1000 atomic basis functions. We first assess in a study of a heme model the accuracy of the strongly- and partially-contracted variant of CD-DMRG-NEVPT2 before embarking on resolving a controversy about the spin ground state of a cobalt tropocoronand complex.