不同模型下HMX晶体结构和性能的MD研究

MD Simulation on the Structure and Properties of Different Models for HMX Crystal

用分子动力学(MD)方法,在COMPASS力场和295K-NPT系综下,对奥克托今(HMX)(4×2×4)和(4×4×4)超晶胞及其沿各自(1 0 0)晶面构成的共6种模型进行了模拟,求得它们的平衡结构、引发键键长分布、引发键连双原子作用能和弹性力学性能。结果表明,引发键呈近似对称的高斯型分布,平均键长(L ave)与实验值很接近;随着体系中原子数目增加,引发键连双原子作用能E N—N单调增加;除柯西压外,各模型的力学性能比较稳定一致。

Molecular dynamics （MD） simulation was applied to investigate cyclotetramethylene （HMX） crystal at 295K using COMPASS force field with the isothermal-isobaric （NPT） ensemble. Six models were considered, which were （4×2×4） and （4×4×4） unit cells and the other models obtained by cutting along their （1 0 0） crystalline surface with different depths. The trigger bond length, the interaction energy between two atoms of trigger bond and the mechanical properties of the HMX crystal were analyzed. Results show that the trigger bond length distribution is approximately symmetrical Gaussian distribution and the average bond length （Lave） is in good agreement with the experimental. The interaction energy （EN—N） between two N atoms of the N—N trigger bond increases monotonously with the increasing of atom numbers in the models, and the mechanical properties are independent of models except for Cauchy pressure.