Local dynamics in a long-chain alkane melt from molecular dynamics simulations and neutron scattering experiments

We make a detailed comparison of the incoherent dynamic structure factors Sinc(q,ω) and Sinc(q,t) for n-C100H202 melts, as determined from time-of-flight (TOF) neutron scattering measurements, with results from atomistic molecular dynamics simulations. Quantitative agreement is seen between simulations and experiments over the dynamic range accessible by the TOF measurements. From detailed analysis of the molecular dynamics trajectories, it is determined that the decay of Sinc(q,t) that occurs between 0.1 and 10 ps is the result of a combination of torsional librations and jumps, with the latter becoming more important with decreasing q.