Molecular dynamics models for sublimation of explosive materials

A clear understanding of sublimation kinetics is critical for developing detection techniques. Sublimation affects the shape and size of small particles as well as the environment. The particle characteristics are essential for various types of measurements including optical response. Molecular dynamic simulations were used to better understand the kinetics of both the condensation of molecules onto and the sublimation of molecules from the surfaces of explosives materials such as 2,4-dinitrotoluene and 2,4,6-trinitrotoluene. These studies were undertaken to better understand the persistence of trace quantities of particles on surfaces to aid efforts to optical detect strategies of explosives as well as physical harvesting approaches such as collection with swabs. Potential-energy-function parameters for the molecular dynamic (MD) simulations are designed and values for the probability of recondensation onto the surface (i.e., sticking coefficient) and the velocity distribution of molecules escaping the particle surface calculated. These values were compared with other experimental and simulation efforts for the studied materials.