Hiroo Totsuji

Yukawa system (dusty plasma) in one-dimensional external fields

Abstract The behavior of the Yukawa system in external one-dimensional force fields is analyzed by molecular dynamics simulation. The formation of layered structures at low temperatures is observed and the relation between the number of layers and characteristic parameters of the system is obtained. Periodic boundary conditions are imposed in two dimensions and deformations of periodic boundaries are allowed in order to reduce the effect of boundaries without placing too much constraint on the symmetry.

Structure and melting of two-dimensional dust crystals

Dust particles in plasmas confined near the boundary between the plasma bulk and the sheath form a two-dimensional system when appropriate conditions are satisfied. To keep dust particles from running away horizontally, the electrostatic potential is usually applied to the electrode surrounding these dusty plasmas and we have finite two-dimensional systems of dust particles. Adopting the Yukawa model for the interaction between dust particles, structures of finite two-dimensional Yukawa systems at low temperatures have been analyzed both by molecular dynamics simulations and variational methods. The effect of the correlation energy between dust particles is shown to play an important role in the formation of the one-body distribution in these systems. Molecular dynamics simulations of large systems typically with 103 to 104 particles have been performed and the behavior of the mean square displacement is obtained for various combinations of characteristic parameters. The results are discussed in relation ...

Structure of dusty plasma in external fields : Simulation and theory

To investigate various structures experimentally observed in dusty plasmas, a Yukawa system in a one-dimensional external field is simulated by molecular dynamics with deformable periodic boundary conditions and constant volume and temperature. At low temperatures, particles are organized into thin layers (sheets) and the number of layers (sheets) changes with the parameters, the whole system being rearranged from nearly equipartitioned layers to other nearly equipartitioned layers. The shell (sheet) model, which has been successful for confined one-component plasmas, is extended to this system and the results of numerical simulations are reproduced accurately. The effect of the cohesive energy in each layer is of essential importance to reproduce discrete changes in the number of sheets.

Molecular dynamics of a Coulomb system with deformable periodic boundary conditions

Abstract Variable shape molecular dynamics is formulated for the one-component plasma and the structural transition from the fcc lattice to the bcc lattice has been observed. It is emphasized that the condition of constant volume should be imposed when deformations of periodic boundary conditions are taken into account.

One-Electron State of a Partially Ionized High-Z Ion

An effective potential of an isolated partially ionized high-Z ion, calculated within the framework of the statistical models of atoms, is injected into the one-electron Schrodinger equation, in view of evaluating the electron density and comparing it with the results of statistical models. Starting from this initial value, a self-consistent electron density is obtained on the basis of the density functional theory, where quantum natures of electrons are fully taken into account.

On the Madelung energy of spherical Coulomb clusters

Abstract We perform large-scale molecular dynamics (MD) simulations of Coulomb clusters in a spherical trapping field. The fast multipole method have been employed to simulate clusters of up to 5×10 4 particles while previous investigations are limited to clusters of less than 5000 particles. It is found that the Madelung energy of bcc clusters with reconstructed surfaces is substantially smaller than the extrapolated values based on the previous results for smaller multilayered icosahedral clusters.

CLASSICAL CHARGED PARTICLE SYSTEMS WITH INTERFACES

Layered structures of finite systems of classical charged particles at low temperatures, confined by external forces of various dimensionalities, are analyzed on the basis of a model which takes the main part of the effect of discreteness of charges into account. The results of previous numerical experiments are reproduced to a good accuracy. Structural transitions at critical values of the characteristic parameter are also predicted and confirmed by our numerical experiments. The roles of intra-layer and inter-layer Coulomb interactions are discussed by comparing our model with known three-dimensional lattices of one-component plasma.

Internal structure of a partially ionized heavy ion. Isolated ion model

An effective potential and an associated electron density in a partially ionized high- Z ion are evaluated within the framework of the Thomas–Fermi–Dirac–Weizsacker statistical model of atoms. The results are then injected as an initial input into the one-electron Schrodinger equation, a procedure based on the density functional theory. The self-consistency between the two approaches is examined. For a partially ionized ion at zero and finite temperatures, a number of bound electrons is counted by a sum over the principal quantum number, which diverges due to the contribution from shallow bound (Rydberg) levels. A truncation of this sum is devised by application of the Planck–Larkin scheme to the Fermi distribution

Physics of ultra high-density plasmas.

A brief review is given on theoretical approaches to physical properties of high-density plasmas which are expected to be realized in the inertial confinement fusion experiments.