Faculty Profiles - TSURUTA Kenji

Papers - TSURUTA Kenji

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Estimation of screening length and electric charge on particles in single-layered dusty plasma crystals (vol 68, art no. 017401, 2003) Reviewed

C Totsuji, MS Liman, K Tsuruta, H Totsuji

PHYSICAL REVIEW E 68 ( 4 ) 2003.10

Estimation of screening length and electric charge on particles in single-layered dusty plasma crystals Reviewed

C Totsuji, MS Liman, K Tsuruta, H Totsuji

PHYSICAL REVIEW E 68 ( 1 ) 499011 2003.7

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER PHYSICAL SOC

Single-layered two-dimensional crystals of dust particles are often observed in dusty plasma experiments and the data on their structure can be obtained by analyzing the images usually taken by charge-cupled device cameras. We give here some formulas for practical purposes of estimating the screening length and the electric charge on a dust particle from the surface density and the radius of such finite two-dimensional dust crystals. The formulas are derived on the basis of our theoretical approach which has been successful in reproducing results of molecular-dynamics simulations on dusty plasmas. An example of application is also shown.

DOI： 10.1103/PhysRevE.68.017401

Other Link： http://orcid.org/0000-0002-1447-2530

Estimation of screening length and electric charge on particles in single-layered dusty plasma crystals Reviewed

Chieko Totsuji, M. Sanusi Liman, Kenji Tsuruta, Hiroo Totsuji

Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics 68 ( 1 ) 4 2003

Language：English Publishing type：Research paper (scientific journal)

Single-layered two-dimensional crystals of dust particles are often observed in dusty plasma experiments and the data on their structure can be obtained by analyzing the images usually taken by charge-cupled device cameras. We give here some formulas for practical purposes of estimating the screening length and the electric charge on a dust particle from the surface density and the radius of such finite two-dimensional dust crystals. The formulas are derived on the basis of our theoretical approach which has been successful in reproducing results of molecular-dynamics simulations on dusty plasmas. An example of application is also shown. © 2003 The American Physical Society.

DOI： 10.1103/PhysRevE.68.017401

Competition between two forms of ordering in finite Coulomb clusters Reviewed

H Totsuji, T Kishimoto, C Totsuji, K Tsuruta

PHYSICAL REVIEW LETTERS 88 ( 12 ) 2002.3

Language：English Publishing type：Research paper (scientific journal) Publisher：AMERICAN PHYSICAL SOC

The lowest-energy state of spherical clusters made up of single-species charged particles in a three-dimensional confining potential is investigated by molecular dynamics simulations for a system size of 5 x 10(3) to 1.2 x 10(5). The energy per particle is compared between shell-structured clusters and spherical finite-bcc lattices with relaxed surfaces. The shell structure in the interior is the lowest-energy configuration for ion numbers lower than about 10(4), while for higher ion numbers, an interior with bcc ordering surrounded by a few shells on the outside has lower energy. The formation of a small bcc lattice (nucleation) in the shell-structured cluster of 2 x 10(4) ions is observed.

DOI： 10.1103/PhysRevLett.88.125002

Structure and Madelung energy of coulomb clusters Reviewed

H Totsuji, T Kishimoto, C Totsuji, K Tsuruta

NON-NEUTRAL PLASMA PHYSICS IV 606 181 - 190 2002

Language：English Publishing type：Research paper (international conference proceedings) Publisher：AMER INST PHYSICS

The ground state of the system of charged particles of one species confined by the three-dimensional, isotropic, and parabolic potential is investigated by molecular dynamics simulations. It is shown that, with the increase of the system size or the number of particles in the system N, the ground state changes from the shell-structured system to the finite bee lattice with reconstructed surface. The critical value of the transition is estimated to be between N = 10(4) and N = 2 x 10(4). The nucleation of the bee lattice in the she I I- structured cluster of 2 x 10(4) ions is observed.

Dusty plasmas under microgravity Reviewed

H Totsuji, C Totsuji, T Kishimoto, K Tsuruta

NON-NEUTRAL PLASMA PHYSICS IV 606 201 - 206 2002

Language：English Publishing type：Research paper (international conference proceedings) Publisher：AMER INST PHYSICS

The structures of Yukawa systems spherically confined under the condition of micro-gravity are analyzed by molecular dynamics simulations. It is shown that the system is separated into the outer and the inner parts and well-developed shells appear in the outer part at low temperatures. In the case of Yukawa mixtures, there occurs the separation of species according to the magnitude of charges.

Collaborative Simulation Grid: Multiscale Quantum-Mechanical/Classical Atomistic Simulations on Distributed PC Clusters in the US and Japan Reviewed

H. Kikuchi, R. K. Kalia, A. Nakano, P. Vashishta, H. Iyetomi, S. Ogata, T. Kouno, F. Shimojo, K. Tsuruta, S. Saini

Proceedings of the IEEE/ACM Supercomputing (SC) 2002 Conference (IEEE Computer Society, Los Alamitos, CA, 2002) 63 - 70 2002

Structure of finite two-dimensional Yukawa lattices: Dust crystals Reviewed

H Totsuji, C Totsuji, K Tsuruta

PHYSICAL REVIEW E 64 ( 6 ) 2001.12

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER PHYSICAL SOC

Dust particles in plasmas are often confined near the boundary between the plasma bulk and the sheath where the gravitation is balanced by electrostatic force. To keep dust particles from running away horizontally, an electrostatic potential is usually applied to the electrode surrounding these dusty plasmas and, under appropriate conditions. we have finite two-dimensional lattices of dust particles. Modeling the interaction between dust particles as the isotropic Yukawa interaction, structures of finite two-dimensional Yukawa systems at low temperatures have been analyzed both by numerical 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.

DOI： 10.1103/PhysRevE.64.066402

Parallel tight-binding molecular dynamics for high-temperature neck formation processes of nanocrystalline silicon carbide Reviewed

K Tsuruta, H Totsuji, C Totsuji

MATERIALS TRANSACTIONS 42 ( 11 ) 2261 - 2265 2001.11

Language：English Publishing type：Research paper (scientific journal) Publisher：JAPAN INST METALS

Tight-binding molecular dynamics (TBMD) simulations are performed to investigate atomic and electronic structures during neck formation processes of nanocrystalline silicon carbide at high temperature. For calculating the electronic energy and forces we use a linear-scaling method (the Fermi-operator expansion method) with a scalable parallel algorithm. The TBMD simulations of collision of SiC nanospheres show that processes of neck formation depend strongly on contact angles between the two grains. Electronic populations at grain boundaries are rather uniform, even in a disordered structure of the grain boundary between misaligned nanospheres, Atomic diffusions at elevated temperature are, on the other hand, quite different in the necks formed with different orientations of particles.

Neck formation processes of nanocrystalline silicon carbide: a tight-binding molecular dynamics study Reviewed

K Tsuruta, H Totsuji, C Totsuji

PHILOSOPHICAL MAGAZINE LETTERS 81 ( 5 ) 357 - 366 2001.5

Language：English Publishing type：Research paper (scientific journal) Publisher：TAYLOR & FRANCIS LTD

Atomistic and electronic structures in the process of intergranular neck formation of nanocrystalline silicon carbide (SiC) have been investigated by a tight-binding molecular dynamics method. An order-N parallel algorithm is employed for efficient calculations of electronic energy and forces. We find that a defect-free neck is formed between SIC nanocrystals aligned along [11 (2) over bar] axis at T = 1000 K. In the case of neck formation between tilted nanocrystals (with an orientation equivalent to a {122}, Sigma = 9 grain boundary), surface reconstruction before sintering, that is Si-Si bond formation, significantly affects the grain-boundary formation. The spatial distribution of the electronic population and the electronic density of states show that structural defects, accompanied by gap states, are formed around the reconstructed regions after the sintering.

On the Madelung energy of spherical Coulomb clusters Reviewed

T Kishimoto, C Totsuji, K Tsuruta, H Totsuji

PHYSICS LETTERS A 281 ( 4 ) 256 - 259 2001.3

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

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 x 10(4) particles while previous investigations are limited to clusters of less than 5000 particles, It is found that the Madelung energy of bce clusters with reconstructed surfaces is substantially smaller than the extrapolated values based on the previous results for smaller multilayered icosahedral clusters. (C) 2001 Elsevier Science B.V. All rights reserved.

Structure of finite two-dimensional Yukawa lattices: Dust crystals Reviewed

Hiroo Totsuji, Chieko Totsuji, Kenji Tsuruta

Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics 64 ( 6 ) 7 2001

Language：English Publishing type：Research paper (scientific journal)

Dust particles in plasmas are often confined near the boundary between the plasma bulk and the sheath where the gravitation is balanced by electrostatic force. To keep dust particles from running away horizontally, an electrostatic potential is usually applied to the electrode surrounding these dusty plasmas and, under appropriate conditions, we have finite two-dimensional lattices of dust particles. Modeling the interaction between dust particles as the isotropic Yukawa interaction, structures of finite two-dimensional Yukawa systems at low temperatures have been analyzed both by numerical 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. © 2001 The American Physical Society.

DOI： 10.1103/PhysRevE.64.066402

Yukawa mixtures with and without gravity Reviewed

H Totsuji, T Kishimoto, C Totsuji, K Tsuruta

PHYSICA SCRIPTA T89 117 - 121 2001

Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SWEDISH ACAD SCIENCES

The structures of systems of particles with repulsive Yukawa interactions are analyzed by molecular dynamics simulations with emphasis on the behavior of Yukawa mixtures. To keep the density of particles with mutual repulsion at finite values, we need some confining mechanism and the latter has strong effects on the structure formation. Under the gravity, the confinement is one-dimensional and we have layered structures. In this case, Yukawa mixtures are separated by the difference in the charge to mass ratios. In the case without gravity, we may have three-dimensional confinement and the behavior of the system may be analyzed by assuming spherical symmetry. We show that there also occurs a separation of species according to the magnitude of charges under the condition of no gravity and we have well-organized structures when the temperature is sufficiently low.

Other Link： http://orcid.org/0000-0002-1447-2530

Initial stages of sintering of TiO<inf>2</inf>nanoparticles: Variable-charge molecular dynamics simulations Reviewed

Ogata S, Iyetomi H, Tsuruta K, Shimojo F, Nakano A, Vashishta P, Kalia R.K, Loong C.-K

Materials Research Society Symposium - Proceedings 634 B7.6.1 - B7.6.6 2001

Yukawa Mixtures with and without Gravity

Hiroo Totsuji, Tokunari Kishimoto, Chieko Totsuji, Kenji Tsuruta

Physica Scripta T89 ( 1 ) 117 - 117 2001

A scalable molecular-dynamics algorithm suite for materials simulations: design-space diagram on 1024 Cray T3E processors Reviewed

F Shimojo, TJ Campbell, RK Kalia, A Nakano, P Vashishta, S Ogata, K Tsuruta

FUTURE GENERATION COMPUTER SYSTEMS-THE INTERNATIONAL JOURNAL OF ESCIENCE 17 ( 3 ) 279 - 291 2000.11

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

A suite of scalable molecular-dynamics (MD) algorithms has been developed for materials simulations. The linear scaling MD algorithms encompass a wide spectrum of physical reality: (i) classical MD based on a many-body interatomic potential model; (ii) environment-dependent, variable-charge MD: (iii) quantum mechanical MD based on the tight-binding method; and (iv) self-consistent quantum MD based on the density functional theory. Benchmark tests on 1024 Gray T3E processors including 1.02-billion-atom many-body and 22 500-atom density functional MD simulations demonstrate that these algorithms are highly scalable. A design-space diagram spanning seven decades of system size and computational time is constructed for materials scientists to design an optimal MD simulation incorporating maximal physical realism within a given computational budget. (C) 2000 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0167-739X(00)00087-X

Other Link： http://orcid.org/0000-0002-1447-2530

Role of atomic charge transfer on sintering of TiO2 nanoparticles: Variable-charge molecular dynamics Reviewed

S Ogata, H Iyetomi, K Tsuruta, F Shimojo, A Nakano, RK Kalia, P Vashishta

JOURNAL OF APPLIED PHYSICS 88 ( 10 ) 6011 - 6015 2000.11

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER INST PHYSICS

The stability of surface structure and space-charge distribution in free TiO2 nanoparticles are investigated for both rutile and anatase phases using a variable-charge interaction potential in which atomic charges vary dynamically depending on their environment. We find the dynamic charge transfer: (i) enhances atomic diffusion at surfaces of the spherical nanoparticles at high temperatures; and (ii) creates additional repulsive force between the two nanospheres through formation of a double-charge surface layer in each nanosphere. The surface diffusion due to the charge transfer clearly distinguishes the two nanospheres with different underlying crystalline structures; the surface diffusion constant of the anatase sphere is almost three times as great as that of the rutile sphere. Variable-charge molecular dynamics simulations are then applied to sintering of two TiO2 nanospheres. It turns out that the enhanced surface diffusion in the anatase nanosphere at high temperatures significantly promotes neck formation between the two spheres. (C) 2000 American Institute of Physics. [S0021-8979(00)08323-7].

DOI： 10.1063/1.1321785

Other Link： http://orcid.org/0000-0002-1447-2530

Sintering, structure, and mechanical properties of nanophase SiC: A molecular-dynamics and neutron scattering study Reviewed

A Chatterjee, RK Kalia, A Nakano, A Omeltchenko, K Tsuruta, P Vashishta, CK Loong, M Winterer, S Klein

APPLIED PHYSICS LETTERS 77 ( 8 ) 1132 - 1134 2000.8

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER INST PHYSICS

Structure, mechanical properties, and sintering of nanostructured SiC (n-SiC) are investigated with neutron scattering and molecular-dynamics (MD) techniques. Both MD and the experiment indicate the onset of sintering around 1500 K. During sintering, the pores shrink while maintaining their morphology: the fractal dimension is similar to 2 and the surface roughness exponent is similar to 0.45. Structural analyses reveal that interfacial regions in n-SiC are disordered with nearly the same number of three- and fourfold coordinated Si atoms. The elastic moduli scale with the density as similar to rho(mu), where mu=3.4 +/- 0.1. (C) 2000 American Institute of Physics. [S0003-6951(00)04334-5].

Strongly coupled nonneutral plasmas: Equilibrium and relaxation in two-component plasmas in Penning-Malmberg trap Reviewed

H Totsuji, K Tsuruta, C Totsuji, K Nakano, T Kishimoto, K Kamon

JOURNAL DE PHYSIQUE IV 10 ( P5 ) 271 - 274 2000.3

Language：English Publishing type：Research paper (scientific journal) Publisher：E D P SCIENCES

The relaxation processes and the equilibrium distribution of two-component nonneutral plasmas in the Penning-Malmberg trap are analyzed by molecular dynamics simulations and theoretical approaches. As an example, mixtures of antiprotons and electrons for antiproton cooling experiments are considered. The relaxation of antiproton energy is calculated based on the rate equations and it is shown that the slow energy transfer between parallel and perpendicular components of strongly magnetized electrons does not affect the whole relaxation process seriously. The equilibrium distribution of each species are obtained by extensive molecular dynamics simulations for various values of parameters and the results are reproduced by theoretical calculations to a good accuracy. The condition for the centrifugal separation is obtained.

DOI： 10.1051/jp4:2000549

Large scale quantum simulations of strongly coupled plasmas on a PC cluster Reviewed

H Totsuji, K Tsuruta, C Totsuji

JOURNAL DE PHYSIQUE IV 10 ( P5 ) 267 - 270 2000.3

Language：English Publishing type：Research paper (scientific journal) Publisher：E D P SCIENCES

As a method of quantum simulation for large systems with surfaces and inhomogenieties, the density functional molecular dynamics is applied to the hydrogen plasma in the domain of liquid metallic hydrogen and the performance of a PC cluster is measured. Usefulness of relatively small scale PC cluter is shown even without much efforts in tuning the programs for parallel computation.

Other Link： http://orcid.org/0000-0002-1447-2530

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