Molecular Structures, Dipole Moments, and Electronic Properties of β-HMX under External Electric Field from First-Principles Calculations

In order to investigate the impact of an external electric field on the sensitivity of beta-HMX explosives, we employ first-principles calculations to determine the molecular structure, dipole moment, and electronic properties of both beta-HMX crystals and individual beta-HMX molecules under varying electric fields. When the external electric field is increasing along the [100], [010], and [001] crystallographic directions of beta-HMX, the calculation results indicate that an increase in the bond length (N1-N3/N1 '-N3 ') of the triggering bond, an increase in the main Q(nitro) (N3, N3 ') value, an increase in the minimum surface electrostatic potential, and a decrease in band gap all contribute to a reduction in its stability. Among these directions, the [010] direction exhibits the highest sensitivity, which can be attributed to the significantly smaller effective mass along the [010] direction compared with the [001] and [100] directions. Moreover, the application of an external electric field along the Y direction of the coordinate system on individual beta-HMX molecules reveals that the strong polarization effect induced by the electric field enhances the decomposition of the N1-N3 bonds. In addition, due to the periodic potential energy of beta-HXM crystal, the polarization effect of beta-HMX crystal caused by an external electric field is much smaller than that of a single beta-HXM molecule.