diffusion monte carlo method
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2021 ◽  
Vol 0 (0) ◽  
Unjong Yu ◽  
Hoseung Jang ◽  
Chi-Ok Hwang

Abstract We develop a last-passage Monte Carlo algorithm on a conducting surface at non-constant potentials. In the previous researches, last-passage Monte Carlo algorithms on conducting surfaces with a constant potential have been developed for charge density at a specific point or on a finite region and a hybrid BIE-WOS algorithm for charge density on a conducting surface at non-constant potentials. In the hybrid BIE-WOS algorithm, they used a deterministic method for the contribution from the lower non-constant potential surface. In this paper, we modify the hybrid BIE-WOS algorithm to a last-passage Monte Carlo algorithm on a conducting surface at non-constant potentials, where we can avoid the singularities on the non-constant potential surface very naturally. We demonstrate the last-passage Monte Carlo algorithm for charge densities on a circular disk and the four rectangle plates with a simple voltage distribution, and update the corner singularities on the unit square plate and cube.

2021 ◽  
pp. 1-6
Nagat Elkahwagy ◽  
Mahmoud Abdelfatah ◽  
Atif Ismail

Potential energy curves for the low-lying electronic states of the title molecules in their neutral and anionic forms have been calculated by means of the diffusion Monte Carlo method. The effect of different trial functionals has been investigated using single determinants constructed from density functional theory (DFT) orbitals with B3LYP, B3PW91, and M06-2X functions. Bond length, vibrational frequency, and electron affinity have also been numerically derived for the selected species and the ground state has been assigned. Spectroscopic parameters obtained are interpreted and compared to their isovalents, shedding some light on further investigations on the selected dimers.

2021 ◽  
Vol 75 (3) ◽  
Gaia Micca Longo ◽  
Carla Maria Coppola ◽  
Domenico Giordano ◽  
Savino Longo

Abstract Computational codes based on the diffusion Monte Carlo method can be used to determine the quantum state of two-electron systems confined by external potentials of various natures and geometries. In this work, we show how the application of this technique in its simplest form, that does not employ complex analytic guess functions, allows to obtain satisfactory results and, at the same time, to write programs that are readily adaptable from one type of confinement to another. This adaptability allows an easy exploration of the many possibilities in terms of both geometry and structure of the system. To illustrate these results, we present calculations in the case of two-electron hydrogen-based species ($$\hbox {H}_{2}$$ H 2 and $$\hbox {H}_{3}^{+})$$ H 3 + ) and two different types of confinement, nanotube-like and octahedral crystal field. Graphic abstract

AIP Advances ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 025225
Yutaka Nikaido ◽  
Tom Ichibha ◽  
Kousuke Nakano ◽  
Kenta Hongo ◽  
Ryo Maezono

2019 ◽  
Vol 33 (21) ◽  
pp. 1950238 ◽  
E. Akaturk ◽  
B. Tanatar

We investigate the properties of a mobile impurity immersed in a two-dimensional (2D) Bose gas at zero temperature using quantum Monte Carlo (QMC) methods. The repulsive boson–boson and impurity-boson interactions are modeled by hard-disk potentials with positive scattering lengths a and b, respectively, taken to be equal to the scattering lengths. We calculate the polaron energy and effective mass for the density parameter na2 [Formula: see text] 1 and the ratio a/b. We find that at low densities perturbation theory adequately describes the simulation results. As the impurity-boson interaction strength increases, the polaron mass is enhanced. Additionally, we calculate the structural properties of the Bose system, such as the impurity-boson pair-correlation function and the change of the density profile around the impurity.

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