Dynamical heterogeneity in a highly supercooled liquid: Consistent calculations of correlation length, intensity, and lifetime

Abstract

We have investigated dynamical heterogeneity in a highly supercooled liquid using molecular-dynamics simulations in three dimensions. Dynamical heterogeneity can be characterized by three quantities: correlation length ξ_4, intensity χ_4, and lifetime τhetero. We evaluated all three quantities consistently from a single order parameter. In a previous study [H. Mizuno and R. Yamamoto Phys. Rev. E 82 030501 (2010)], we examined the lifetime τhetero(t) in two time intervals t=τα and τngp, where τα is the α-relaxation time and τngp is the time at which the non-Gaussian parameter of the Van Hove self-correlation function is maximized. In the present study, in addition to the lifetime τhetero(t), we evaluated the correlation length ξ_4(t) and the intensity χ_4(t) from the same order parameter used for the lifetime τhetero(t). We found that as the temperature decreases, the lifetime τhetero(t) grows dramatically, whereas the correlation length ξ_4(t) and the intensity χ_4(t) increase slowly compared to τhetero(t) or plateaus. Furthermore, we investigated the lifetime τhetero(t) in more detail. We examined the time-interval dependence of the lifetime τhetero(t) and found that as the time interval t increases, τhetero(t) monotonically becomes longer and plateaus at the relaxation time of the two-point density correlation function. At the large time intervals for which τhetero(t) plateaus, the heterogeneous dynamics migrate in space with a diffusion mechanism, such as the particle density.