Dielectric properties of a-RDX and its vibrational modes: Quantum chemistry calculations*

The effect of an external electric field on the dielectric constant of crystalline a-RDX and vibrational modes thereof are studied using quantum chemistry methods. An artificial neural network method was employed to obtain an improved set of parameters for the XDM dispersion corrections. It is shown that the empirical XDM corrections in the improved form make it possible to reproduce the crystal properties and vibrational modes in excellent agreement with available experimental data. The dielectric constant is computed as a function of an external electric field. The obtained results are fit to the Booth model and a satisfactory agreement is achieved.