Equilibration of concentrated hard-sphere fluids Article uri icon

abstract

  • We report a systematic molecular dynamics study of the isochoric equilibration of hard-sphere fluids in their metastable regime close to the glass transition. The thermalization process starts with the system prepared in a nonequilibrium state with the desired final volume fraction for which we can obtain a well-defined nonequilibrium static structure factor S0(k;). The evolution of the α-relaxation time τα(k) and long-time self-diffusion coefficient DL as a function of the evolution time tw is then monitored for an array of volume fractions. For a given waiting time the plot of τα(k;,tw) as a function of exhibits two regimes corresponding to samples that have fully equilibrated within this waiting time [≤(c)(tw)] and to samples for which equilibration is not yet complete [≥(c)(tw)]. The crossover volume fraction (c)(tw) increases with tw but seems to saturate to a value (a)?(c)(tw→?)?0.582. We also find that the waiting time tweq() required to equilibrate a system grows faster than the corresponding equilibrium relaxation time, tweq()?0.27[ταeq(k;)] 1.43, and that both characteristic times increase strongly as approaches (a), thus suggesting that the measurement of equilibrium properties at and above (a) is experimentally impossible. © 2011 American Physical Society.

publication date

  • 2011-01-01