Benchmark all-electron ab initio quantum Monte Carlo calculations for small molecules

TL;DR

This paper evaluates the efficiency, accuracy, and precision of all-electron quantum Monte Carlo methods for small molecules, demonstrating high correlation energy recovery and insights into error sources.

Contribution

It introduces an algorithm to enforce the electron-nucleus cusp condition and provides comprehensive benchmarking of quantum Monte Carlo calculations on the G2 molecular set.

Findings

Recovers 95% of correlation energy on average

Reproduces bond energies with a mean absolute deviation of 3.2 kcal/mol

Provides insights into error cancellation and nodal surface errors

Abstract

We study the efficiency, precision and accuracy of all-electron variational and diffusion quantum Monte Carlo calculations using Slater basis sets. Starting from wave functions generated by Hartree-Fock and density functional theory, we describe an algorithm to enforce the electron-nucleus cusp condition by linear projection. For the 55 molecules in the G2 set, the diffusion quantum Monte Carlo calculations recovers an average of 95% of the correlation energy and reproduces bond energies to a mean absolute deviation of 3.2 kcal/mol. Comparing the individual total energies with essentially exact values, we investigate the error cancellation in atomization and chemical reaction path energies, giving additional insight into the sizes of nodal surface errors.