Predicting the FCI energy of large systems to chemical accuracy from restricted active space density matrix renormalization group calculations

TL;DR

This paper introduces a new extrapolation method, DMRG-RAS-X, based on a power law error scaling, enabling highly accurate energy predictions for complex strongly correlated systems with reduced computational effort.

Contribution

The paper derives and validates a power law error scaling for DMRG-RAS, leading to a parameter-free, robust extrapolation method that achieves chemical accuracy in large, strongly correlated systems.

Findings

Achieves chemical accuracy for Chromium dimer and dicarbon with large basis sets.

Successfully applies to complex systems like FeMoco with lower computational cost.

Demonstrates robustness and reliability across multiple challenging examples.

Abstract

We theoretically derive and validate with large scale simulations a remarkably accurate power law scaling of errors for the restricted active space density matrix renormalization group (DMRG-RAS) method [arXiv:2111.06665] in electronic structure calculations. This yields a new extrapolation method, DMRG-RAS-X, which reaches chemical accuracy for strongly correlated systems such as the Chromium dimer, dicarbon up to a large cc-pVQZ basis, and even a large chemical complex like the FeMoco with significantly lower computational demands than previous methods. The method is free of empirical parameters, performed robustly and reliably in all examples we tested, and has the potential to become a vital alternative method for electronic structure calculations in quantum chemistry, and more generally for the computation of strong correlations in nuclear and condensed matter physics.