On Predicting the Crystal Structure of Energetic Materials from Quantum Mechanics

A quantum-mechanically-based potential energy function that describes interactions of dimers of the explosive cyclotrimethylenetrinitramine (RDX) is used to predict polymorphic structures of crystalline RDX. The potential was first used in crystal structure prediction methods which generate polymorphs of RDX and provide a 0 K ordering in energy. The 13 low energy-structures generated by crystal structure prediction methods were subsequently subjected to isothermal-isostress molecular dynamics (NsT MD) simulations to establish stability rankings and assess effect of inclusion of temperature. For both crystal structure prediction methods and molecular dynamics simulations, the low-energy polymorph corresponds to the experimental structure with crystallographic parameters in outstanding agreement with experiment.