Calculation of decomposition products from components of gunpowder by using ReaxFF reactive force field molecular dynamics and thermodynamic calculations of equilibrium composition

Abstract

The major combustion products from munitions containing nitro-based propellants are water, carbon monoxide, carbon dioxide, hydrogen and nitrogen. In addition, compounds including hydrogen cyanide, ammonia, methane, nitrogen oxides, benzene, acrylonitrile, toluene, furan, aromatic amines, benzopyrene, and various polycyclic aromatic hydrocarbons are detected in minor concentrations. The literature shows that the thermodynamic prediction of the major decomposition products agrees fairly well with the measurements. However, poor agreement is found for the minor species. We have studied the thermal decomposition products of the main gunpowder ingredients. Each of the components nitrocellulose, nitroglycerine and the nitrate ester stabilizers diphenylamine and ethyl centralite were thermally decomposed with ReaxFF reactive force field molecular dynamics and equilibrium thermodynamics. The molecular dynamics results for the major decomposition products from nitrocellulose were partly consistent with measurements. Compared to the thermodynamic calculations, the molecular dynamics simulations agreed considerably better with experimental results for minor species like hydrogen cyanide. The nitrate ester stabilizers are the main sources for ammonia and aromatic combustion products, whereas hydrogen cyanide is produced from nitrocellulose as well as from the stabilizers when gunpowder is combusted.