Japanese

Tsuneyuki Research Group


Current Research Areas

In our laboratory, material properties under extreme conditions are studied by utilizing computer simulation methods based on the theory of electronic state, the molecular dynamics, and the first-principle electronic state calculations. The word "first-principle" means solving fundamental equations which rule electrons with basic physical constants such as Planck constants and eliminating empirical parameters. The importance of the first-principle calculation is that it can be applied to the system such as extremely high-pressure condition, complicated bulk surface/interface state, and nanostructures where experimental observations are difficult or sufficient information cannot be obtained by experiments.

Here, recent principal research topics are introduced aiming at undergraduate students.

Development of Calculation Methodologies

  • Density Functional Theory
  • First-Principles Molecular Dynamics
  • Path-Integral Molecular Dynamics
  • Quantum Monte Carlo
  • Transcorrelated Method
  • Structural Exploration
Sturcture Optimization
Structural exploration over saddle points of the potential-energy surface


Optical Processes in Solids

  • Numerical investigation of the stabilization mechanism of excitonic N-body complexes.
  • The amorphization of phase change materials by irradiating ultrashort pulse laser
Figure
Excitonic complexes in diamond. We showed the stability of complexes circled by solid lines by numerical calculations.


Dielectric

  • Origin of ferroelectricity
  • Properties associated with the vacancy in a dielectric
Figure
Electron carriers doped in a barium titanate


Physics of Hydrogen in Solids

  • Hydrogen in Metals and Semiconductors
  • Hydrogen-Bonded Materials
  • Solid Hydrogen
  • Quantum Effect

Quantum Distributions of Muon in Muonium State in Crystalline Silicon
Phys. Rev. Lett. 81, 1873-1876 (1998).

Superconductivity

  • Ab initio Prediction of Superconducting Transition Temperature
Gap function of MgB2
Gap function of MgB2


Magnetism

  • Electronic and spin properties at metal-semiconductor interfaces

Interface structure of Nd magnet


Thermal Conductivity

  • Thermal Conductivity Calculation
Lattice thermal conductivity calculation with NEMD
Thermal Conductivity Calculation with Non-Equilibrium Molecular Dynamics


Surface and Interface Science

  • Electronic and spin properties at metal-semiconductor interfaces
Spin-polarized state at a nitride-boride interface
Spin-polarized wave function at the AlN/MgB2 interface
Phys. Rev. Lett. 106, 047201 (2011).

High-Pressure Physics

  • Phase Transition under High Pressure
  • Mineral Properties
  • High-Pressure Synthesis

Nuclei distribution of solid hydrogen under high pressure
Nature 404, 259-262 (2000).