Abstract

หัวข้อเรื่อง

	Abstract
	While the statistical mechanics of system in thermalequilibrium is a well established discipline, nonequilibrium systems are fundamentally much less well understood, even though most natural phenomena fall into the latter category. In particular, there is as yet no nonequilibrium analog for the systematic formalism of Gibbs ensemble. Rather than use the anlytic approach as a tool to attack the nonequilibrium problem, this studies is restricted to the utilizing the computational tool via computer Monte Carlo simulations. We have performed the simulations of the noneqilibrium vacancy-driven disordering process of an initially phase segregated binary alloys system, which is rapidly heated to a temperature above criticality, T_c. To quantify the evolution of the system, we measure the number of broken bonds, A(L,t), as a function of time and system size. This disorder parameter allows us to identify three temporal regimes, distinguished by the distribution of the vacancies through the system. The temporal growth of A during the latter regime is captured by the exponent ~ 0.5. If the final temperature is infinite, i.e., T=K , the motion of the vacancies is a simple Brownian random walk. For finite temperature T ³1.5 T_c, we observe that these exponents still hold with some deviation. Even though interparticle interactions now play a role, correlations in the system are still short-ranged, so that the vacancy still performs a random walk if viewed on a length scale which exceeds the correlation length.