钝感高能炸药三氨基三硝基苯高温高压下热力学性质的分子动力学模拟研究

A molecular dynamics simulation of thermodynamic properties of 1,3,5-triamino-2,4,6-trinitrobenzene under high pressure and high temperature

热力学性质是钝感高能炸药1,3,5-三氨基-2,4,6-三硝基苯(TATB)爆轰性质和安全性评估分析的重要参数.由于结构的复杂性,TATB炸药尚缺乏系统的实验和理论计算结果.结合全原子力场和分子动力学的方法,本文系统研究了不同温度和压力条件下TATB的力学性质和热力学参数,得到了弹性模量、德拜温度等随温度、压力的变化情况,并与实验进行了对比分析.结果表明:在0—50 GPa外部压力下,TATB晶体保持力学稳定,弹性常数和弹性模量随压力升高而增大,各向异性程度随压力升高而减小,泊松比和延展性则受压力的影响较小;随温度的升高,TATB的力学稳定性逐渐下降,有发生力学失稳的可能,各弹性常数随温度升高而逐渐减小,各向异性程度也随之减小;TATB的声速和德拜温度同样随着压力升高而增大,平均声速从0 GPa下的1833 m/s,增加到10 GPa下的3143 m/s,德拜温度由0 GPa下的254 K增加到10 GPa的587 K.TATB热膨胀系数的计算表明,在200—500 K温度常压情况下,其体热膨胀系数为35.9×10-5K^(-1),与实验数据符合较好.

Equation of states and thermodynamic properties of insensitive high explosive 1, 3, 5-triamino-2, 4, 6-trinitrobenzene（TATB） are investigated by using molecular dynamics simulation, where an all-atom force field for TATB developed by Richard H. Gee and isothermal-isobaric molecular dynamics（NPT-MD） methods are used. Results obtained include thermal expansion coefficient, elastic constants, tensile modulus, and debye frequency under high temperature and high pressure. The volume coefficient of thermal expansion for crystalline TATB is calculated in a temperature range of 200 to 500 K and at atmospheric pressure. The result, 35.9 × 10^-5K^-1, is in general agreements with the experimental results.Results of elastic constants show that the crystalline TATB is an orthotropic material. The calculated elastic constants decrease with increasing temperature in the range from 0 to 450 K, while increase as the pressure increases from 0 to50 GPa. And the bulk modulus at 300 K is 11.32 GPa, which is in good agreement with the available experimental results. Results obtained above have been compared with available experimental data, and also discussed in relation to the previous calculations. The above results are better than existing ones gained by others. In addition, the elastic anisotropy becomes lower with increasing temperature or pressure. As the temperature goes up to 400 K, the lattice becomes unstable. The sound speed and Debye frequency are calculated by using the data of elastic constants at different pressures. This provides a theoretical basis to calculate the anisotropic thermal conductivity for crystalline TATB.