Structural heterogeneity in supercooled liquids and glasses

Molecular-dynamics (MD) simulation has been used to study the dynamical properties of supercooled liquids near the glass transition temperature. We have found the dynamical heterogeneity for microscopic and semi-macroscopic time scales. Careful analyses with a large-size molecular dynamics simulation have been made to demonstrate well-defined correlations among motions of atoms in time windows corresponding to alpha and beta relaxations. These correlated motions of atoms of particular interest may lead to the spatial-temporal heterogeneity which are attributed to particular dynamical origins. These heterogeneities originate from linearly correlated jump motions up to about the order of ten atoms which occurs in semi-macroscopic time scale and linearly correlated motions of atoms composed of the order of more than hundred atoms which lasts only for microscopic time scale. These two correlated motions are connected in supercooled liquids and glasses. (C) 1998 Elsevier Science B.V. All rights reserved.