Yasushi Shibuta

Can completely homogeneous nucleation occur? Large scale molecular dynamics simulations performed on a graphics-processing-unit rich supercomputer can shed light on this long-standing issue. Here, a billion-atom molecular dynamics simulation of homogeneous nucleation from an undercooled iron melt reveals that some satellite-like small grains surrounding previously formed large grains exist in the middle of the nucleation process, which are not distributed uniformly. At the same time, grains with

The phase transition between liquid and solid phases in body-centered cubic (bcc) metal nanoparticles of iron, chromium, molybdenum, and tungsten with size ranging from 2000 to 31,250 atoms was investigated using a molecular dynamics simulation. The nucleation from an undercooled liquid droplet was observed during cooling in all nanoparticles considered. It was found that a nucleus was generated near one side of the particle and solidification spread toward the other side the during nucleation p

The temperature dependences of the energy and structure of the symmetric tilt boundary of bcc and fcc iron were investigated by molecular dynamics simulation. A large energy cusp was observed at the bcc(112)‹110›Σ3 and fcc(111)‹110›Σ3 grain boundary plane, which is a twin boundary, whereas it was not observed at the bcc(111)‹110›Σ3 plane in spite of it having the lowest Σ-value. The grain boundary energy increased at the temperature close to the melting point except for the grain boundary planes

Thanks to the recent progress in high-performance computational environments, the range of applications of computational metallurgy is expanding rapidly. In this paper, cutting-edge simulations of solidification from atomic to microstructural levels performed on a graphics processing unit (GPU) architecture are introduced with a brief introduction to advances in computational studies on solidification. In particular, million-atom molecular dynamics simulations captured the spontaneous evolution

Homogeneous nucleation from an undercooled iron melt is investigated by the statistical sampling of million-atom molecular dynamics (MD) simulations performed on a graphics processing unit (GPU). Fifty independent instances of isothermal MD calculations with one million atoms in a quasi-two-dimensional cell over a nanosecond reveal that the nucleation rate and the incubation time of nucleation as functions of temperature have characteristic shapes with a nose at the critical temperature. This in

A novel phase-field model for electrochemical processes, in which cations were driven by an electrostatic potential coupled with a thermodynamic potential, was formulated from a variation of the Ginzburg–Landau free-energy functional. Using this model, an electrodeposition process of copper deposits from copper-sulfate solution was studied using a phase-field simulation. The dependence of the growth velocity of the electrode on the applied voltage was examined in a one-dimensional system. Then,