Multireference linearized Coupled Cluster theory for strongly correlated systems using Matrix Product States

TL;DR

The paper introduces MPS-LCC, a multireference linearized coupled cluster method using matrix product states, achieving high accuracy and computational efficiency for strongly correlated electronic systems, including solids and complex molecules.

Contribution

It presents a novel MPS-LCC approach that combines accuracy and efficiency, outperforming traditional methods in strongly correlated systems.

Findings

MPS-LCC achieves high accuracy comparable to DMRG.

It offers several orders of magnitude speedup over DMRG.

Outperforms standard multireference quantum chemistry methods in benchmarks.

Abstract

We propose a multireference linearized coupled cluster theory using matrix product states (MPS-LCC) which provides remarkably accurate ground-state energies, at a computational cost that has the same scaling as multireference configuration interaction singles and doubles (MRCISD), for a wide variety of electronic Hamiltonians. These range from first-row dimers at equilibrium and stretched geometries, to highly multireference systems such as the chromium dimer and lattice models such as periodic two-dimensional 1-band and 3-band Hubbard models. The MPS-LCC theory shows a speed up of several orders of magnitude over the usual DMRG algorithm while delivering energies in excellent agreement with converged DMRG calculations. Also, in all the benchmark calculations presented here MPS-LCC outperformed the commonly used multi-reference quantum chemistry methods in some cases giving energies in excess of an order of magnitude more accurate. As a size-extensive method that can treat large active spaces, MPS-LCC opens up the use of multireference quantum chemical techniques in strongly-correlated \emph{ab-initio} Hamiltonians, including two and three-dimensional solids.