Wen-Bing Zhang

Influence of external field on diffusion-limited aggregation

Abstract The influence of external electric field on diffusion-limited aggregation (DLA) has been investigated by computer simulations. When the parameter λ increases from 0 to ∞, the morphology of aggregates changes from pure DLA to chain-like pattern gradually, where λ stands for the relative strength of field-induced dipolar interaction to thermal energy. The structure transition is the transition between a prototype disorder structure and a relative order one in essence. The reason of the transition is the interaction controlling systems changes from thermal force to field-induced dipolar interactions with λ rising.

Short-time dynamics behavior at the gas–liquid critical point

Abstract The dynamic relaxation process for the two dimension fluid at the critical point was studied, by using the constant pressure and constant temperature (NPT) molecular dynamics (MD). The system was initially at the state of very high temperature and of the density little higher than the critical density, and then it was quenched to the state of the critical temperature and critical pressure. The initial increase of the density was observed. The new dynamic exponent θ has been obtained and it manifests the universal short-time dynamic behavior also exists in the fluid phase.

STRUCTURE AND GROWTH OF THE CLUSTER IN GAS-LIQUID TRANSITION OF TWO-DIMENSIONAL FLUID

Molecular dynamics simulations have been performed for a two-dimensional fluid with truncated Morse potential quenched into the two-phase region. The cluster size and shape were used to study the domain growth and structure. The power-law growth of the characteristic length scale, which was calculated through the mean cluster size, i.e., l∼ta with a=12 and 13, was observed in the late stage. The fractal dimension was obtained from the scaling relationship of the gyration radius of the clusters with the cluster numbers. The structure factors showed scaling relationship when scaled with the characteristic length. It is also found that the domain structures are sensitive to temperature, and the thermal noise influences the growth exponent for the dilute system.

COLLECTIVE MOTION AND MASS EFFECT IN A SUPERCOOLED LIQUID

Collective motion and mass effect of atomic diffusion have been studied by molecular dynamics simulation on a ternary system. Small mass effect has been found, which shows about ten particles take part in the collective diffusion in the supercooled liquid.

DEPENDENCE OF THE GLASS TRANSITION TEMPERATURE ON DENSITY IN A SOFT SPHERE SYSTEM WITH MORSE POTENTIAL

The glass transition for the soft sphere system with Morse potential was investigated based on molecular dynamics simulation and partition function analysis. The dependence of the glass transition temperature on the density and the softness of the potential was obtained.

Molecular dynamics simulation of the energy localization of an impurity solved in 1D lattice

By means of molecular dynamics simulations we have investigated local energy excitations of impurities with different types (stiffness, size or mass) solved in a one-dimensional lattice. The basic configuration studied is that an impurity particle is imbedded into a chain which consists of host particles interacting via a modified Morse potential. The results show that in thermal equilibrium the impurity may lead to local energy excitations at the impurity site. The stiffness and size impurities bring about a localization of the potential energy, while the mass impurity causes that of the kinetic energy. The variation of energies with the impurity parameters and temperature is obtained and explained by the soliton picture of a Toda lattice.

Electrical Resistivity and Metal–Non-Metal Transition of Liquid MgxSn1—x and Mg2(PbySn1—y) Alloys

Electrical resistivities of the liquid Mg x Sn 1-x and Mg 2 (Pb y Sn 1-y ) alloys with 0 ≤ x, y < 1 have been measured as functions of composition. A very high and sharp resistivity maximum occurs at the stoichiometric composition Mg 2 Sn for both systems. The metal-non-metal transition appears around this composition. If these liquid alloys are roughly considered to be a system consisting of metallic and non-metallic components the plots of the resistivity versus metallic component fraction are similar for liquid Mg x Sn 1-y and Mg 2 (Pb y Sn 1-y ).