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

Molecular dynamics (MD) calculations of cis-1,4-polybutadiene in bulk amorp hous phase were performed under constant pressure and constant temperature conditions. The static and dynamic properties were evaluated from the resul ts of MD calculations. The obtained density and coefficient of thermal expa nsion are in good agreement with experimental data. The feature of the calc ulated static structure factor is similar to the observed one. Molecular mo tion is examined with mean square displacements and intermediate scattering functions. An onset of a new motion, which Corresponds to so-called fast p rocess, was clearly observed in the temperature dependence of the mean squa re displacement above 100 K. The dynamic structure factors obtained by the Fourier transformation of the intermediate scattering functions are compare d with those obtained from quasielastic neutron scattering measurements. Th e peaks corresponding to the elastic scattering and the low energy excitati on at around 2 meV are reproduced in the dynamic structure factors. The exc essive intensity observed in the dynamic structure factor, which correspond s to the fast process, is also reproduced above 140 K in our simulation. (C ) 2001 Elsevier Science Ltd. All rights reserved.