Reorientational jump dynamics and its connections to hydrogen bond relaxation in molten acetamide: an all-atom molecular dynamics simulation study.

Abstract

Here we report results from our molecular dynamics simulations on orientational relaxation and hydrogen bond dynamics of molten acetamide. Signatures for orientational jumps have been detected with jump barrier estimated to be ∼0.7 kBT. Simulated orientational relaxations indicate deviations from hydrodynamics and this deviation has been ascribed to the detected orientational jumps. Simulated free energy surfaces obtained at various distances between the rotating acetamide and its initial and final H-bond acceptors have been found to be symmetric double-well in nature at the transition state. H-bond relaxation times obtained from our simulations corroborate well with the time scales associated with the jump and waiting time distributions, suggesting an interrelationship between jump dynamics and H-bond fluctuations. Jump angle distributions are asymmetric and depict long tails extending to large angles.