Interfacial Interaction between Double (010) Faces of β-HMX

摘要

The interfacial interaction between double (010) faces of β-HMX was computationally discussed for the first time to simulate an explosive crystal against external mechanical stimuli probably causing some interfacial movements including compression, stretching rupture, shear slide, and twist. The results show that: (1) in the equilibrium structure of the HMX crystal, the distance between two neighboring layers close to the crystal surface is longer than that in the crystal bulk, showing the looser molecules on or near the surface; (2) a point of inflection of the distance between the centroids of the two blocks (d) composing the (010) interface appears at d=3.3 A, where there are the biggest surface areas of the interfacial HMX molecules and three extremums of van der Waals, valence and electrostatic interaction energy (AE), respectively. And it also leads to non-monotonous changes of △E-d correlation of valence interaction during both shear sliding and twisting; (3) the highest sliding and twisting barriers along the (010) face in case of no crystal crack, can make each interfacial HMX molecule share averagely the increased energy 48 and 140 kl/mol, respectively. From a comparison of these increased energy with the apparent activation energy of thermal decomposition of HMX crystal, 140 kJ/mol, we deduce that the shear sliding along (010) face without crystal rupture is probably allowable, but the twisting is forbidden; and (4) the change of total interaction energy during sliding and twisting is dominated by that of van der Waals interaction energy.