Assessment report of research on development activities in FY 2021 Activity; "Computational Science and Technology Research" (Result and in-advance evaluation)

Center for Computational Science & e-Systems

JAEA-Evaluation 2022-003, 61 Pages, 2022/11

JAEA-Evaluation-2022-003.pdf:1.42MB
JAEA-Evaluation-2022-003-appendix(CD-ROM).zip:6.16MB

Japan Atomic Energy Agency (hereinafter referred to as "JAEA") consults an assessment committee, "Evaluation Committee of Research Activities for Computational Science and Technology Research" (hereinafter referred to as "Committee") for result and in-advance evaluation of "Computational Science and Technology Research", in accordance with "General Guideline for the Evaluation of Government Research and Development (R&D) Activities" by Cabinet Office, Government of Japan, "Guideline for Evaluation of R&D in Ministry of Education, Culture, Sports, Science and Technology" and "Regulation on Conduct for Evaluation of R&D Activities" by the JAEA. In response to the JAEA's request, the Committee assessed the research program of the Center for Computational Science and e-Systems (hereinafter referred to as "CCSE"). The Committee evaluated the management and research activities of the CCSE based on explanatory documents prepared by the CCSE, and oral presentations with questions-and answers.

Path integral Brownian chain molecular dynamics; A Simple approximation of quantum vibrational dynamics

Shiga, Motoyuki

Journal of Computational Chemistry, 43(27), p.1864 - 1879, 2022/10

https://doi.org/10.1002/jcc.26989

A new approximate method for quantum vibrational dynamics (Brownian chain molecular dynamics: BCMD) based on the path integral method is proposed. Conventional methods such as centroid molecular dynamics and ring polymer dynamics cannot correctly calculate quantum vibration spectra under low temperature conditions. Thus, I introduce an over-damped Langevin equation for the non-centroid degrees of freedom of atoms to suppress unphysical resonances and vibrational rotational couplings, which are the source of the problem. I verify this approximation through applications to infrared absorption spectra of light and heavy water. I also demonstrate the feasibility of ab initio BCMD simulations by the combination with electronic structure theory.

VR extension of particle-based remote visualization application

Kawamura, Takuma; Sakamoto, Naohisa*

Proceedings of 41st JSST Annual International Conference on Simulation Technology (JSST 2022) (Internet), p.266 - 269, 2022/09

Visualization of the large CFD dataset in remote locations by VR, especially using volume rendering, is one of the issues in the visualization field. The visualization library KVS supports PBVR, a unique particle-based visualization method suitable for large-scale data, and we have developed an extension of KVS for VR. In this paper, we present a design for VR extension of CS-PBVR, a remote visualization application based on KVS. The developed CS-PBVR for VR is then applied to test data and shown to be capable of VR visualization at interactive frame rates.

Extended X-ray absorption fine structure spectroscopy measurements and molecular dynamics simulations reveal the hydration structure of the radium(II) ion

Yamaguchi, Akiko; Nagata, Kojiro*; Kobayashi, Keita; Tanaka, Kazuya; Kobayashi, Toru; Tanida, Hajime; Shimojo, Kojiro; Sekiguchi, Tetsuhiro; Kaneta, Yui; Matsuda, Shohei; et al.

iScience (Internet), 25(8), p.104763_1 - 104763_12, 2022/08

https://doi.org/10.1016/j.isci.2022.104763

no abstracts in English

Artificial neural network-based path integral simulations of hydrogen isotope diffusion in palladium

Kimizuka, Hajime*; Thomsen, B.; Shiga, Motoyuki

Journal of Physics; Energy (Internet), 4(3), p.034004_1 - 034004_13, 2022/07

https://doi.org/10.1088/2515-7655/ac7e6b

Artificial neural network-based interatomic potential for a system of palladium and hydrogen was developed, and path integral molecular dynamics simulations were performed to study the quantum diffusion of hydrogen isotopes in palladium crystals. Diffusion coefficients of light and heavy hydrogen were calculated over a wide temperature range of 50-1500 K to clarify the difference in diffusion mechanisms at low and high temperatures.

One-week lesson of numerical calculations in Julia language

Nagai, Yuki

Julia Programming for Numerical Computation; A One-week Course, 244 Pages, 2022/06

no abstracts in English

Optimization of phase field variables in gas-liquid two-phase flow problems

Sugihara, Kenta; Onodera, Naoyuki; Idomura, Yasuhiro; Yamashita, Susumu

Keisan Kogaku Koenkai Rombunshu (CD-ROM), 27, 5 Pages, 2022/06

The phase-field method has been successfully applied to various multi-phase flow problems as an interface tracking method for gas-liquid interfaces. However, the accuracy of the phase-field method depends on hyper-parameters, which are empirically adjusted for each problem. The phase-field method sustains sharp interfaces by the balance between the numerical viscosity of the advection term and the interface modification by the diffusion and anti-diffusion terms. Based on this fact, we propose a method for deriving the optimal hyper-parameters in a non-empirical manner by performing a basic error analysis of the interface advection.

Performance measurement of an urban wind simulation code with the Locally Mesh-Refined Lattice Boltzmann Method over NVIDIA and AMD GPUs

Asahi, Yuichi; Onodera, Naoyuki; Hasegawa, Yuta; Shimokawabe, Takashi*; Shiba, Hayato*; Idomura, Yasuhiro

Keisan Kogaku Koenkai Rombunshu (CD-ROM), 27, 5 Pages, 2022/06

We have ported the GPU accelerated Lattice Boltzmann Method code "CityLBM" to AMD MI100 GPU. We present the performance of CityLBM achieved on NVIDIA P100, V100, A100 GPUs and AMDMI100 GPU. Using the host to host MPI communications, the performance on MI100 GPU is around 20% better than on V100 GPU. It has turned out that most of the kernels are successfully accelerated except for interpolation kernels for Adaptive Mesh Refinement (AMR) method.

Effect of uniaxial tensile strain on binding energy of hydrogen atoms to vacancy-carbon-hydrogen complexes in -iron

Hirayama, Shintaro*; Sato, Koichi*; Kato, Daiji*; Iwakiri, Hirotomo*; Yamaguchi, Masatake; Watanabe, Yoshiyuki*; Nozawa, Takashi*

Nuclear Materials and Energy (Internet), 31, p.101179_1 - 101179_9, 2022/06

https://doi.org/10.1016/j.nme.2022.101179

no abstracts in English

Fourier interpolation method in phase space of Hamiltonian systems

Sasa, Narimasa

Journal of the Physical Society of Japan, 91(5), p.054001_1 - 054001_8, 2022/05

https://doi.org/10.7566/JPSJ.91.054001