RELAXATION DYNAMICS IN A LATTICE-GAS - A TEST OF THE MODE-COUPLING THEORY OF THE IDEAL GLASS-TRANSITION

By means of computer simulations we investigate the dynamical behavior of a binary lattice-gas mixture with short-range interactions in orde r to provide a stringent test of mode-coupling theory (MCT). The dynam ics of the particles is given by Monte Carlo-like moves that change th e positions of the particles and binary collisions that change the vel ocities. By monitoring the self part of the van Hove correlation funct ion we find the low-temperature dynamics to be glasslike. In accordanc e with MCT, the imaginary part of the dynamic susceptibility chi'' sho ws a well-defined alpha peak whose high-frequency wing follows a von S chweidler law with an exponent that is independent of temperature. The low-frequency wing of the peak follows a different power-law dependen ce that corresponds to a power law of the form -P + A/tdelta (A, P, de lta > 0) in the self part of the intermediate scattering function F(s1 )(k, t). In agreement with MCT we find that the diffusion constant for one of the two types of particles, the relaxation-times of F(s1)(k,t) , the location of the alpha peak in the susceptibility, and the prefac tor of the von Schweidler law all have a power-law dependence on tempe rature, (T - T(c))gamma, for T > T(c) at constant density. As predicte d by the theory, the critical temperatures T(c) for the different quan tities are the same within the statistical error. However, in contradi ction to MCT, the critical exponents gamma vary from one quantity to a nother. The value of the Lamb-Mossbauer factor shows qualitatively the wave-vector dependence predicted by MCT. The self part of a second ki nd of correlation function exhibits the two power laws predicted by MC T for the high- and low-frequency wings of the beta relaxation. We sho w that, in the vicinity of the minimum in chi'', the scaling behavior predicted by MCT holds. However, the location of this minimum at a giv en temperature depends on the quantity investigated, contrary to the p redictions of MCT. Moreover, the value of chi'' at this minimum exhibi ts a power-law dependence on temperature with an exponent that is sign ificantly larger than the one predicted by MCT. We also find that the height of the alpha peak as well as the total energy per particle have a power-law dependence on temperature and that the corresponding crit ical temperatures are close to those obtained for the other quantities .