Chủ tịch danh dự Chủ tịch Hội nghị Ban Tổ chức Ban ... - Viện Vật lý

College of Education, Hue University, 34 Le Loi Street, Hue City,
Vietnam
We built efficient 3D Poisson solvers based on post-BICGSTAB
algorithms: BICGSTAB (L), enhanced BICGSTAB (L).
Calculations are performed on Windows computers. It is showed
that these solvers work very well in uniform grids. Convergent
characteristics are improved very significantly and memory size is
minimized. Consequently, the solvers are hundred times faster than
solvers based on LU decomposition, Gauss’s elimination, Jacobi
and Gauss-Seidel iteration algorithms.
Báo cáo Treo
105. 3D Monte Carlo Simulation of GaAs p-i-n Diodes Taking into
Account the Near Coulomb Interaction between Electrons and Holes
Dinh Nhu Thao and Tran Thien Lan
College of Education, Hue University, 34 Le Loi Street, Hue City,
Vietnam
This paper presents 3D simulation of carrier dynamics in GaAs p-in
diodes taking into account the near Coulomb interaction between
electrons and holes. The device simulation is carried out with
various electric fields of 70, 100 and 130 kV/cm. The simulation
results show that the interaction gives a correction of 10^6 V/m,
equal to 1/10 the total electric field in the devices. The results also
show that the velocity overshoot and the velocities obtained are
nearly the same in both cases: with and without the near Coulomb
interaction. This indicates that the near Coulomb interaction has no
important role in carrier dynamics and it can be ignored in usual
calculations.
Báo cáo Treo
106. 3D Monte Carlo Simulation of Carrier Dynamics and THz
Radiation from GaAs p-i-n Diodes
Dinh Nhu Thao and Le Hoai Linh
College of Education, Hue University, 34 Le Loi Street, Hue City,
Vietnam
In this paper we present 3D simulation of carrier dynamics and THz
radiation from GaAs p-i-n diodes. We built a 3D device simulator
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with a Poisson solver based on BiCGSTAB algorithm. The results
are consistent with 1D simulation ones. They confirm effect of 1D
model in considering p-i-n diodes. They also show that THz
radiation are really from LO phonons but from TO phonons, and the
obvious coupling of light from carrier acceleration and LO phonons.
Báo cáo Treo
107. Density Functional Based Study on Zinc Oxide Nanoparticles
Vu Ngoc Tuoc and Nguyen Viet Minh
Hanoi University of Science and Technology
We have performed the Density Functional Tight Binding (DFTB)
study on the structural properties of Zinc Oxide Nanoparticles (NP),
focusing on the effects induced by the surfaces and quantum size
effect. Effects of surface relaxation and surface stress which is
absent in atomistic model are taken carefully into account. The
studying Nanoparticle's size range up to 2.5nm. We illustrated the
structural properties changes by decreasing NP sizes while the
typical length of surface relaxation (~1 nm) remain unchanged and
comparable with the particle size. The NP electronic properties, i.e.
Density of State (DOS), charge transfer in hetero-bond also showed
the deviation from bulk material value.
Báo cáo Treo
108. Computer Simulation of Diffusion in Disordered Systems with
many Particles
P.K.Hung and T.V.Mung
Department of Computational Physics, Hanoi University of
Technology, 1 Dai Co Viet, Hanoi
Understanding the microscopic mechanism of diffusion in
amorphous materials remains a challenge in physics and material
science. Previous simulations of diffusion of particle alone in
disordered system show two specific features which are common
for the dynamic in amorphous materials, however, the presence of
large number of impurity has not been considered yet. In the present
paper we shows a new simulation technique enabling to consider
the diffusion of many impurities in disordered system. The
Tp. Hồ Chí Minh, 02-06/8/2010
simulation in linear chain consisting of several thousand sites has
been conducted. The concentration of impurities varies in the range
from 0 to 0.2. Two-level sates are applied for site and transition
energies. The simulation result indicates a significant influence of
the impurity concentration for systems where the disorder degree is
strong. This result could explain qualitatively the concentration
effect which is experimentally observed for diffusion of light atoms
in amorphous alloys.
Báo cáo Treo
109. Structure and Dynamics of Gold-Silicon Alloy by Molecular
Dynamics Simulation
T. L. Thuy. Nguyen (1), Noel Jakse (1) and Alain Pasturel
(1,2)
1. Laboratoire Sciences et Ingénierie, Matériaux et Procédés, UMR
CNRS-INPG-UJF 5266, PHELMA-Grenoble-INP, BP 75, 38402
Saint Martin d'Hères Cedex, France.
2. Laboratoire de Physique et Modélisation des Milieux Condensés,
UMR-CNRS 5493, Maison des Magistères, BP 166 CNRS, 38042
Grenoble-Cedex09, France.
A series of molecular dynamics simulations for the liquid,
supercooled states of Au-Si alloy at the eutectic composition are
presented. The interactions are described via a modified embeddedatom
model (MEAM) for which several parameter sets exist.. The
structural properties, namely, the pair-correlation functions,
coordination numbers and the abundance of bonded pairs from the
common neighbor analysis, and the dynamic properties through the
self-diffusion coefficients are calculated and the results are
compared to ab initio molecular dynamics data. An analysis of the
various parameterizations is provided and improvements are
proposed.
Báo cáo Treo
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110. Accelerated MD Programm using CUDA Technology
Nguyen Thu Nhan, Nguyen Thi Thanh Ha, and Pham Khac
Hung
Hanoi University of Technology, 1 Dai Co Viet, Hai Ba Trung, Ha
Noi
Molecular dynamic (MD) simulation is proven to be an important
tool to study the structure as well as the physical properties at
atomic level in material science. However, it requires a huge
computing time and hence limits the ability to treat a large scale
simulation. In this paper we present a solution to speed up the MD
simulation using CUDA technology (Compute Unified Device
Architecture). We used the GeForce GTS 250 card with Version
2.30. The simulation is implemented for Lennard-Jones systems
with periodic boundary conditions which consist of 1024, 2048,
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