A Study of High-Pressure Behavior of β-HMX
|Keywords||Density functional theory Local density approximation Band gap|
HMX usually stands for octahydro-l,3,5,7-tetranitro-l,3,5,7-tetrazocine or octogen which is white crystal-line solid. Due to its unusual insensitivity to high temperatures, shock, and impact, HMX has been considered as one of the most important high explosives. Understanding structure in molecular details and bonding behaviors under extreme condition has become essential to improve this particular area of science and technology. It’s the bridge between microscopic atoms or molecules and macroscopic condensed matters.In the electronic structure calculations, density functional theory(DFT) calculations are applied. The local density approximation (LDA) exchange-correlation potential has been used in the calculation. We analyze the electronic structures and the intra-molecular geometries of theβ-HMX crystal with the hydrostatic compression up to 40 GPa. Also, the pressure dependences of the cell volume, the lattice constants and the molecular geometry of solidβ-HMX are presented and discussed.1. The unit cell volume forβ-HMX obtained by the LDA calculations are show the same tendency as that of experiments.2. Variations of bond lengths in p-HMX crystal as a function of pressure (0-40GPa) are shown in the study. It can be found that N-N bond and C-N bond are more compressible.3. From the variations of bond lengths inβ-HMX crystal as a function of pressure (0-40GPa) we found that the sharply decrease of N2-N1-O2 and N1-N2-C2 is caused by the decrease of N1-N2. But, N2-N1-O1 and N1-N2-C1 increase a little.4. From the band gap, we find it decrease slowly with the augment of pressure. From our study, we find the DFT-LDA gives quite good results.