Multireference linearized coupled cluster theory for strongly correlated systems using matrix product states

Area of Science:

• Quantum Chemistry
• Computational Physics
• Condensed Matter Theory

Background:

• Accurate calculation of ground-state energies is crucial for understanding molecular and material properties.
• Strongly correlated systems and large active spaces pose significant challenges for traditional quantum chemistry methods.
• Existing methods like Density Matrix Renormalization Group (DMRG) can be computationally expensive.

Purpose of the Study:

• To develop a computationally efficient and accurate method for calculating ground-state energies in multireference systems.
• To extend the applicability of quantum chemical techniques to strongly correlated ab initio Hamiltonians and solid-state models.
• To provide a robust alternative to existing methods for electronic structure calculations.

Main Methods:

• Development and application of multireference linearized coupled cluster theory using matrix product states (MPSs-LCC).
• Benchmarking MPSs-LCC against Density Matrix Renormalization Group (DMRG) and other multi-reference quantum chemistry methods.
• Testing the method on a diverse range of systems, including first-row dimers, chromium dimer, and Hubbard models.

Main Results:

• MPSs-LCC achieves remarkably accurate ground-state energies with computational costs comparable to multireference configuration interaction singles and doubles.
• The method demonstrates speed-ups of several orders of magnitude compared to the standard DMRG algorithm.
• MPSs-LCC energies show excellent agreement with converged DMRG calculations and outperform other common multi-reference methods, sometimes by over an order of magnitude.

Conclusions:

• MPSs-LCC is a powerful and efficient method for accurate electronic structure calculations, particularly for challenging multireference systems.
• Its size-extensivity and ability to handle large active spaces enable the application of advanced quantum chemical techniques to complex problems.
• This method opens new avenues for studying strongly correlated phenomena in molecules and materials, including extended solids.