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 β-HMX explosives, we employ first-principles
calculations to determine the molecular structure, dipole moment,
and electronic properties of both β-HMX crystals and individual
β-HMX molecules under varying electric fields. When the external
electric field is increasing along the [100], [010], and [001] crystallographic
directions of β-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 Qnitro (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 β-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 β-HXM crystal, the polarization
effect of β-HMX crystal caused by an external electric field
is much smaller than that of a single β-HXM molecule.