INTERFACE DYNAMICS IN A MEAN-FIELD LATTICE-GAS MODEL - SOLUTE TRAPPING, KINETIC COEFFICIENT, AND INTERFACE MOBILITY

In a recent paper we showed that we can obtain dendritic growth in a m ean-field lattice gas model. The equation of motion, derived from a lo cal master equation, is a generalized Cahn-Hilliard equation. In the p resent paper, we study the isothermal dynamics of planar interfaces in this model. Stationary interface states advancing with constant veloc ity are investigated. We present numerical results as well as a contin uum approximation that gives an analytic expression for the shape corr ection in the limit of small interface velocities. We observe departur e from local equilibrium at the interface and solute trapping. The ass ociated kinetic coefficients are calculated. The two effects are found to be related. We finally give an expression for the interface mobili ty and derive a relation between this mobility and the kinetic coeffic ients. Furthermore, we show that there occur oscillations of the growt h velocity and density waves in the two hulk phases during the advance of the interface. This is related to the discrete dynamics using the theory of area-preserving maps as proposed by Pandit and Wortis.