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Boosting the accuracy and speed of quantum Monte Carlo: Size consistency and time step

Zen, A; Sorella, S; Gillan, MJ; Michaelides, A; Alfè, D; (2016) Boosting the accuracy and speed of quantum Monte Carlo: Size consistency and time step. Physical Review B - Condensed Matter and Materials Physics , 93 (24) , Article 241118. 10.1103/PhysRevB.93.241118. Green open access

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Abstract

Diffusion Monte Carlo (DMC) simulations for fermions are becoming the standard for providing high-quality reference data in systems that are too large to be investigated via quantum chemical approaches. DMC with the fixed-node approximation relies on modifications of the Green's function to avoid singularities near the nodal surface of the trial wave function. Here we show that these modifications affect the DMC energies in a way that is not size consistent, resulting in large time-step errors. Building on the modifications of Umrigar et al. and DePasquale et al. we propose a simple Green's function modification that restores size consistency to large values of the time step, which substantially reduces time-step errors. This algorithm also yields remarkable speedups of up to two orders of magnitude in the calculation of molecule-molecule binding energies and crystal cohesive energies, thus extending the horizons of what is possible with DMC.

Type: Article
Title: Boosting the accuracy and speed of quantum Monte Carlo: Size consistency and time step
Open access status: An open access version is available from UCL Discovery
DOI: 10.1103/PhysRevB.93.241118
Publisher version: http://dx.doi.org/10.1103/PhysRevB.93.241118
Language: English
Additional information: Copyright © 2016 American Physical Society. The published version of record is also available at http://dx.doi.org/10.1103/PhysRevB.93.241118
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
URI: https://discovery.ucl.ac.uk/id/eprint/1497587
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