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We study solitary wave propagation in periodic dimer granular chains of beads with the same material but different sizes by binary collision approximation. This kind of chain which is called N:1 dimer consists of pairs of N big beads and one small bead. First we present a method to map the actual chain into an effective chain, then use the binary collision approximation to obtain the transmitted solitary wave speed, the total time taken by the pulse to pass through the chain, and the frequency of oscillation of the small particle. Frequency of oscillation, which increases with the decrease of the radius of the small particle, is analytically obtained. And the results are in excellent agreement with numerical results. For the total time of the pulse passing through the chain, the results of theoretical analysis is in good agreement with numerical results when N 2. The relative error seems no change with the chain length but becomes larger with the increase of the value of N.

Using the plane-wave pesudopotential (PWPP) method within the generalized gradient approximation (GGA), we investigate the hydrostatic pressure induced effect on the structural, electronic and elastic properties of cubic perovskites SrSnO3 and SrZrO3. The pressure dependence of the lattice constants, some indirect and direct band gaps, the upper valence bandwidths, the elastic stiffness constants and the aggregate elastic moduli, as well as the Debye temperature are investigated. Our calculated ground-state results are in good agreement with the available experimental and theoretical data.

The oscillation phenomena for granular mixture within a vertically vibrated container are investigated with the event-driven method. The container consists of two rooms with equal size separated by a clapboard with certain height，and two kinds of granules with the radius of one twice as larger as the other are used. Investigation results indicate that the period of oscillation of granula sharply increases with the decrease of the ratio of density between two kinds of particles. The relations of the ratio of density to the ratio of vertical height of the two kinds of particles are calculated, which shows that the main factor of granular oscillation is not the “Brazil nut effect” or “reverse Brazile nut effect”. The granular temperature is calculated and found to be relevant to oscillations of mixture. When the temperature of the small particle is above a certain value, oscillations of granular mixture occur. According to hydromechanical equations proposed by Viridi et al., these equations are correspondly modified and may explain the relations between the period of oscillation and the ratio of granular density.

Based on reaction limited aggregation model, we have investigated the dynamical process of film epitaxial growth in the presence of surfactant. The results ind icate that there are differences between the growth processes of fractal island and compact island. The growth exponents of fractal islands are greater than 1, which that of compact islands are less than 1. On the other hand, “dead" atom d ensity increases linearly with the coverage in the process of the fractal island growth, but the relations between the density and the coverage are nonlinear in the compact island situation.