Molecular simulations of free surfaces, and crystallization phenomena of molecular crystals.

摘要

In this thesis, a method to determine mechanical properties of polymers is presented that relies on direct sinusoidal loading. A new method for calculating surface mobilities of simple Lennard-Jones mixtures is also presented. It is found that the surfaces of model glasses are orders of magnitude more mobile than the bulk of the materials, both for small molecules and for polymers. The second part of the thesis deals with molecular crystallization phenomena. Studies of Ortho Terphenyl serve to demonstrate the stability of glasses. Under seeded conditions, however, these materials crystallize at temperatures lower than the glass transition temperature. These studies indicate that, consistent with experiments, such molecules may crystallize at rates that are disconnected from the diffusivity of the systems. It is also demonstrated that the amorphous states of hard spheres are a result of localized disorder, which is identified in this study with fivefold symmetry.