Dynamic Heterogeity in Glass-forming Polymers in terms
of Non-Gaussian Parameter (NGP)

Dynamic Heterogeneity

T-dependence of NGP

NGP and fragility

It is considered that glass-forming materials are dynamically heterogeneous. Many studies have been performed to elucidate the dynamic heterogeneity.

Comparison of T-dependence of NGP between theoretical calculation and experimental data, showing 4 monomers are localized in the Boson peak mode.

NGP increases with decreasing fragility index m.

What is non-Gaussian parameter?

Prog. Theor. Phys. Suppl., 126, 133-140 (1997)

J. Non-cryst. Solids, 235/237, 212-218 (1998)

AIP Conference Series, 469, 350-357 (1999)

Phys. Rev., B61, R6451-R6454 (2000)

Under the Gaussian approximation, dynamic scattering law S(Q,?) at ?=0 is described as exp(-aQ2). In glass-forming materials the Gaussian approximation is broken down due to dynamic heterogeneity, and S(Q,?=0) is written in the following form, including non-Gaussian parameter A0. This corresponds to the standard deviation of mean square displacement <u2>.