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Speeding up ab initio diffusion Monte Carlo simulations by a smart lattice regularization

2020; American Physical Society; Volume: 101; Issue: 15 Linguagem: Inglês

10.1103/physrevb.101.155106

2469-9977

Kousuke Nakano, Ryo Maezono, Sandro Sorella,

Thermal properties of materials

One of the most significant drawbacks of the all-electron ab initio diffusion Monte Carlo (DMC) is that its computational cost drastically increases with the atomic number ($Z$), which typically scales with ${Z}^{\ensuremath{\sim}6}$. In this study, we introduce a very efficient implementation of the lattice regularized diffusion Monte Carlo (LRDMC), where the conventional time discretization is replaced by its lattice space counterpart. This scheme enables us to conveniently adopt a small lattice space in the vicinity of nuclei, and a large one in the valence region, by which a considerable speedup is achieved, especially for large atomic number $Z$. Indeed, the computational performances of the improved LRDMC can be theoretically established based on the Thomas-Fermi model for heavy atoms, implying the optimal ${Z}^{\ensuremath{\sim}5}$ scaling for all-electron DMC calculations. This improvement enables us to apply the DMC technique even for superheavy elements ($Z\ensuremath{\ge}104$), such as oganesson ($Z=118)$, which has the highest atomic number of all synthesized elements so far.