Molecular dynamics simulation of cis-1,4-polybutadiene. 1. Comparison with experimental data for static and dynamic properties

Abstract

Molecular dynamics (MD) calculations of cis-1,4-polybutadiene in bulk amorphous phase were performed under constant pressure and constant temperature conditions. The static and dynamic properties were evaluated from the results of MD calculations. The obtained density and coefficient of thermal expansion are in good agreement with experimental data. The feature of the calculated static structure factor is similar to the observed one. Molecular motion is examined with mean square displacements and intermediate scattering functions. An onset of a new motion, which corresponds to so-called fast process, was clearly observed in the temperature dependence of the mean square displacement above 100 K. The dynamic structure factors obtained by the Fourier transformation of the intermediate scattering functions are compared with those obtained from quasielastic neutron scattering measurements. The peaks corresponding to the elastic scattering and the low energy excitation at around 2 meV are reproduced in the dynamic structure factors. The excessive intensity observed in the dynamic structure factor, which corresponds to the fast process, is also reproduced above 140 K in our simulation.