Auxiliary-field quantum Monte Carlo study of TiO and MnO molecules

TL;DR

This paper applies a phaseless auxiliary field quantum Monte Carlo method to calculate the binding energies of TiO and MnO molecules, demonstrating good agreement with experimental data and highlighting its potential for studying correlation effects in materials.

Contribution

The study introduces and validates a phaseless auxiliary field quantum Monte Carlo approach for transition metal oxides, showing its effectiveness and robustness.

Findings

Binding energies agree well with experiments.

Method is robust for correlation effects in materials.

Comparable to diffusion Monte Carlo results.

Abstract

Calculations of the binding energy of the transition metal oxide molecules TiO and MnO are presented, using a recently developed phaseless auxiliary field quantum Monte Carlo approach. This method maps the interacting many-body problem onto a linear combination of non-interacting problems by a complex Hubbard-Stratonovich transformation, and controls the phase/sign problem with a phaseless approximation relying on a trial wave function. It employs random walks in Slater determinant space to project the ground state of the system, and allows use of much of the same machinery as in standard density functional theory calculations, such as planewave basis and non-local pseudopotentials. The calculations used a single Slater determinant trial wave function obtained from a density functional calculation, with no further optimization. The calculated binding energies are in good agreement with experiment and with recent diffusion Monte Carlo results. Together with previous results for sp-bonded systems, the present study indicates that the phaseless auxiliary field method is a robust and promising approach for the study of correlation effects in real materials.