Exact special twist method for quantum Monte Carlo simulations

• Autores: Dagrada, Mario; Karakuzu, Seher; Vildosola, Veronica Laura; Casula, Michele; Sorella, Sandro
• Año de publicación: 2016
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Quantum Monte Carlo; Finite size effects; Strongly correlated systems
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

We present a systematic investigation of the special twist method introduced by Rajagopal et al. [Phys. Rev. B 51, 10591 (1995)PRBMDO0163-182910.1103/PhysRevB.51.10591] for reducing finite-size effects in correlated calculations of periodic extended systems with Coulomb interactions and Fermi statistics. We propose a procedure for finding special twist values which, at variance with previous applications of this method, reproduce the energy of the mean-field infinite-size limit solution within an adjustable (arbitrarily small) numerical error. This choice of the special twist is shown to be the most accurate single-twist solution for curing one-body finite-size effects in correlated calculations. For these reasons we dubbed our procedure "exact special twist" (EST). EST only needs a fully converged independent-particles or mean-field calculation within the primitive cell and a simple fit to find the special twist along a specific direction in the Brillouin zone. We first assess the performances of EST in a simple correlated model such as the three-dimensional electron gas. Afterwards, we test its efficiency within ab initio quantum Monte Carlo simulations of metallic elements of increasing complexity. We show that EST displays an overall good performance in reducing finite-size errors comparable to the widely used twist average technique but at a much lower computational cost since it involves the evaluation of just one wave function. We also demonstrate that the EST method shows similar performances in the calculation of correlation functions, such as the ionic forces for structural relaxation and the pair radial distribution function in liquid hydrogen. Our conclusions point to the usefulness of EST for correlated supercell calculations; our method will be particularly relevant when the physical problem under consideration requires large periodic cells.
Fil: Dagrada, Mario. Universite Pierre et Marie Curie; Francia
Fil: Karakuzu, Seher. Scuola Internazionale Superiore di Studi Avanzati; Italia
Fil: Vildosola, Veronica Laura. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Investigación y Aplicaciones No Nucleares. Gerencia Física (Centro Atómico Constituyentes). Proyecto Tandar; Argentina
Fil: Casula, Michele. Universite Pierre et Marie Curie; Francia. Centre National de la Recherche Scientifique; Francia
Fil: Sorella, Sandro. Scuola Internazionale Superiore di Studi Avanzati; Italia