Modeling complex intramolecular processes using constrained molecular dynamics

Abstract

A phenomenological approach based on constrained molecular dynamics for modeling complex intramolecular processes on the characteristic time scale of intermolecular interactions is presented. One feature of this approach is that it allows modeling of energy transfer between intermolecular degrees of freedom and internal molecular modes on a longer time scale than is possible using more detailed methods. In addition, by using time-dependent or conditional constraints, this approach can be extended for the modeling of molecular dissociation and subsequent energy release in energetic materials. In this paper this approach is used to construct a model for energy transfer between lattice modes and the internal modes of a large molecular group. The mathematical properties of constrained molecular dynamics that are important for accurately modeling internal processes on an intermolecular time scale are examined. Results of simulations of shocks propagating through a reactive crystal using the present model demonstrate the utility of constrained molecular dynamics for modeling energy transfer in complex systems are presented.