Influences of pressure on structural and electronic properties of four types of HMX

The crystal and electronic structures of four polymorphs of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) from 0 to 30 GPa were investigated by using density functional theory. The obtained structural parameters based on the GGA-PBE+TS calculations are in agreement with experimental results at ambient pressure. As the pressure increases, the volumes of the four types of HMX decrease monotonically and the band gaps gradually decrease without any significant discontinuity. Moreover, the peaks of the density of states become lower and the bandwidths become broader, which indicate that the hybridizations become strong under pressure. From the results, we suggest that the impact sensitivity for HMX becomes more and more sensitive with increasing pressure.