MOLECULAR-DYNAMICS SIMULATIONS OF MACROSCOPIC VIBRATIONS ON COOLING OF SUPERHEATED POLYETHYLENE CRYSTALS

In this paper a discussion is given of the change of density with time and temperature within a crystal of 192 (CH2)(50) chains, simulated b y molecular dynamics computations at temperatures from 65 to 425 K. Th e highest temperatures exceed the melting temperature (about 365 K). O n simulation for times of up to 100 ps the temperature dropped through the melting temperature, permitting the study of the behavior of the crystal during initial melting, followed by limited recrystallization. In these short times only a limited number of chains on the surface c an begin to coil and melt conformationally, but there is an indication of a disordering transition. A better comparison with experimental da ta on density, expansivity and speed of sound is possible.