TNAZ的第一原理分子力学力场

The First Principle Force Field for Energetic Material TNAZ

分子力学力场的适用性和准确性是制约分子模拟应用的瓶颈。本文依照TEAM力场的研发思想,推导了1,3,3-三硝基氮杂环丁烷(TNAZ)的全原子第一原理分子力学力场。键参数和电荷参数拟和自第一性原理计算结果,范德华参数迁移自文献报道并通过模拟TNAZ液相密度和蒸发焓进行了优化。通过分子力学、分子动力学模拟,计算了TNAZ分子的气相、液相和晶相性质对参数进行了验证。验证结果显示气相分子的结构、能量、振动性质,液相的密度、蒸发焓,晶体结构、晶格能等结果与实验测定一致。同时预测了TNAZ晶体的热胀性质、等温压缩等性质。模拟得到的热胀曲线在整个凝聚相内显示出三个具有不同热胀率的区段。其中300K下TNAZ晶体体积较400K下减小约13%,与实验观测吻合。300K下等温压缩到10GPa,体积减小约28%,与文献报道的理论值一致。

The availability and accuracy of molecular force fields limit their application scope. In this work, a first principle and all-atom force field for 1,3,3-trinitroazetidine （TNAZ） was developed based on the TEAM method. The valence parameters and atomic partial charges were derived by fitting to ab initio data. The van der Waals （VDW） parameters were taken from the literature and optimized using experimental densities and vaporization enthalpies of liquids. In order to validate the force field, the properties of TNAZ in gas, solid and liquid states were calculated. It has been shown that the force field is highly accurate in predicting the above properties, which include molecular structures, vibration frequencies, liquid densities, vaporization enthalpies, crystal structures, and lattice energies. The isobaric and isotherm curves of the condensed phases were calculated. The isobaric curves can be partitioned into three regions. The volume of crystalline TNAZ at 300 K is about 13% smaller than that at 400 K, which is consistent with the experimental observation. The volume of crystalline TNAZ is reduced by about 28% when the system is compressed under 10 GPa pressure and 300 K, which is consistent with other theoretical predictions.