Computational Study of the Influence of Voids Onto the Elastic Moduli of Crystalline RDX
The goal of this study is to address the influence of voids in the crystal onto the sensitivity of the energetic material RDX. The mechanisms of detonation initiation are not well understood at this time. Voids may promote energy transfer from crystalline vibrational modes to intramolecular degrees of freedom, and thus facilitate bond-breaking processes. Recently, this group studied the distribution of the energy of a mechanical shock wave in a system of crystalline RDX, in particular in the vicinity of a void using molecular dynamics simulations based on a classical force field, including intra- and intermolecular degrees of freedom. New work seeks to evaluate the elastic properties, i.e. bulk modulus and the elements of the tensor of elastic moduli, for RDX. Particular focus is on the influence of voids onto these moduli. The computations involve series of geometry optimizations of extended crystalline systems with voids to find the bulk modulus from the curvature of the energy of the system, and to test out the curvature of energy with re[ect to specific deformation directions. Parts of these projects were done in 2012, but the researchers expect that more computations become necessary as the data reveal their structure.
Further, the PI uses computational time for a different project which studies cloud formation from a water vapor phase using a finite-element model currently under development.