MOLECULAR-DYNAMICS ANALYZED IN TERMS OF CONTINUOUS MEASURES OF DYNAMIC HETEROGENEITY

We analyse the relaxation data of a supercooled liquid in terms of phi (t)=integral g(ln tau) phi(t/tau) d ln tau using a Kohlrausch, William s, and Watts (KWW) type integral kernel phi(t/tau) with exponent, beta (hom), which serves for varying the degree of homogeneity inherent in the response of each relaxer, while the concomitant g(ln tau) defines the extent of dynamic heterogeneity. The simulated time dependence of solvation free energies as a function of beta(hom) is compared with ex perimental solvation dynamics data, nu(t) and sigma(inh)(t) derived fr om time resolved inhomogeneously broadened optical lineshapes. The exp erimental findings indicate 0.8 less than or equal to beta(hom) less t han or equal to 1, which states that the dynamical nature of the relax ation process is dominated by the spatial variation of relaxation time s, while the possible extent of homogeneous dispersion remains small. (C) 1998 Elsevier Science B.V. All rights reserved.