A deterministic alternative to the full configuration interaction quantum Monte Carlo method

TL;DR

This paper introduces a highly efficient deterministic method that achieves chemical accuracy and efficiently computes excited states, offering an alternative to the stochastic full configuration interaction quantum Monte Carlo approach.

Contribution

The paper presents a deterministic method that replaces stochastic sampling in FCIQMC, enabling accurate and efficient calculations for complex systems and excited states.

Findings

Achieves chemical accuracy for various systems including Cr2.

Efficiently computes excited state energies with benchmark results.

Provides a deterministic alternative to stochastic FCIQMC.

Abstract

Development of exponentially scaling methods has seen great progress in tackling larger systems than previously thought possible. One such technique, full configuration interaction quantum Monte Carlo, is a useful algorithm that allows exact diagonalization through stochastically sampling determinants. The method derives its utility from the information in the matrix elements of the Hamiltonian, along with a stochastic projected wave function, to find the important parts of Hilbert space. However, the stochastic representation of the wave function is not required to search Hilbert space efficiently, and here we describe a highly efficient deterministic method to achieve chemical accuracy for a wide range of systems, including the difficult Cr$_{2}$ dimer. In addition our method also allows efficient calculation of excited state energies, for which we illustrate with benchmark results for the excited states of C$_{2}$.