Computational materials physics is a branch of physics which elucidates properties of materials with computers. Properties of materials originate from the atomic structures: which kind of atom the material consists of and by how the atoms are assembled into the materials. Therefore Yoshimoto has studied structure of materials, especially, the changes of the structures, by using the first principles electronic structure calculations, which is an excellent method in computational materials physics to treat the structure of materials. In addition, he performed various joint-research projects utilizing the technology for the first-principles electronic structure calculations.
Highlight of research
- Simulation of melting of silicon using multiorder-multithermal method.
Melting/crystallization of silicon is studied by a developed variant of multicanonical method. Silicon repeatedly goes back and forth between liquid state and crystal state. This is very hard to reproduce in ordinal constant temperature molecular dynamics (MD) simulation. In the ordinal MD, melted silicon is rarely crystallized perfectly again.
This simulation is actually a virtual one and it does not correspond to a specific temperature. Nevertheless it includes whole thermodynamics of silicon, and by using “reweighting”, we can deduce physics at any temperature from this single simulation run. Moreover the simulation itself is accelerated because the relaxation time is shortened in the multicanonical MD.
YY, JCP 125, 184103 (2006)
- First-principles electronic structure calculation on nitrogen atoms adsorbed on copper surface
Nitrogen atoms adsorbed on copper (001) surface are spontaneously assembled into a regular structure, which is a kind of surface compound, on the surface. Its scanning Tunneling Microscope (STM) image was simulated by a first-principles calculation.
Copper nuclei and nitrogen nuclei are colored by green and red, respectively. The blue isosurfaces are for the electron density of the system. The yellow surface above them is the simulated STM image. Vs is the sample bias of the STM in [V] and z is the height from the center of the slab in [Angstrom].
YY, S. Tsuneyuki, Surf. Sci. 514, 200 (2002)