Scaling laws for the 2d 8-state Potts model with Fixed Boundary Conditions

We study the effects of frozen boundaries in a Monte Carlo simulation near a first order phase transition. Recent theoretical analysis of the dynamics of first order phase transitions has enabled to state the scaling laws governing the critical regime of the transition. We check these new scaling laws performing a Monte Carlo simulation of the 2d, 8-state spin Potts model. In particular, our results support a pseudo-critical beta finite-size scaling of the form beta(infinity) + a/L + b/L^2, instead of beta(infinity) + c/L^d + d/L^{2d}. Moreover, our value for the latent heat is 0.294(11), which does not coincide with the latent heat analytically derived for the same model if periodic boundary conditions are assumed, which is 0.486358...Comment: 10 pages, 3 postscript figure

Defect and impurity effects on the initial growth of Ag on Si(111)

Step and impurity effects on the initial growth of a thin film have been demonstrated in the ({radical}3 {times} {radical}3)R30{degree} domain growth of Ag on Si(111) using high angular resolution LEED. Anisotropy in the {radical}3 domain shape and growth during deposition are found on the stepped Si(111) with the preferential growth along the step edge direction. The {radical}3 superlattice grows with coverage principally by domain coalescence at the temperature T {approximately} 450{degree}C and is self-similar at different coverages (scaling) as observed on a flat Si(111). The size distribution is shown to follow a Gamma distribution by a simple model calculation. A dramatic change in the growth mechanism is observed when oxygen impurities ({le}0.02 ML) appear. The {radical}3 domains in the presence of impurities grow with coverage more randomly and isotropically in contrast with the step edge effects and coalescence is inhibited. As a result, the {radical}3 superlattice stays in a microdomain morphology without long range order. 17 refs., 6 figs