精确计算TATB分子间相互作用能并重新认识其作用本质

Accurate calculation of the intermolecular interaction energy of the TATB and rediscover the nature of the interaction

TATB炸药的钝感性质与其分子间强烈的相互作用密切相关,目前尚难以用实验方法直接准确地测定其分子间相互作用能.已发表的理论研究工作受当时计算方法和条件限制,计算结果误差较大、充满矛盾.本文用B3PW91-D3BJ/def2-TZVPP方法优化了TATB二聚体可能存在的六种构型的几何结构并作振动频率分析,发现仅有三种稳定构型,即氢键构型A,堆叠构型B和C,用MP2/def2-TZVPP方法重新优化了这三种构型的几何结构参数,并用于CCSD(T)/CBS方法计算,得到分子间相互作用能分别为A:-6.20,B:-15.45,C:-15.65 kcal/mol,CCSD(T)/CBS计算中发现构型B和C的高级校正项大约是分子间相互作用能的50%,是MP2方法不可能准确预测TATB二聚体堆叠构型分子间相互作用能的原因;本文还用新一代能量分解方法ALMO-EDA分析了TATB分子间相互作用本质,发现对于堆叠构型B和C,除了色散作用之外,静电吸引对决定TATB二聚体中的几何结构十分重要,TATB高能炸药良好的钝感性质起源于其分子间较强静电吸引的驱动和定向,使之形成稳定的堆叠结构,其稳定性来源于色散和静电的协同作用.

The insensitive property of TATB explosive is related to its strong intermolecular interaction. So far, it has been difficult to directly and accurately determine the intermolecular interaction energy by experimental methods. The theoretical calculation results that have been published are limited by the calculation methods and conditions at that time, and the errors are large and contradictory. In this paper, the B3 PW91-D3 BJ/def2-TZVPP method was used to optimize the six possible configurations of TATB dimer and the vibration frequency analysis was performed. We found that there are only three stable configurations, namely hydrogen-bonded configuration A, stacked configurations B and C. The geometric parameters of the three configurations used in the CCSD(T)/CBS calculations have been optimized again using the MP2/def2-TZVPP method. The intermolecular interaction energies obtained with CCSD(T)/CBS method are A:-6.20, B:-15.45, C:-15.65 kcal/mol. During the CCSD(T)/CBS calculation, it was found that the high level correction terms for configurations B and C are about 50% of the binding energy, which is why the MP2 method cannot accurately predict the intermolecular interaction energy of the TATB dimer stack configuration. We also analyzed the nature of TATB intermolecular interaction using the new generation energy decomposition method, ALMO-EDA, and found that for the stacked configurations B and C, except for the dispersion effect, the electrostatic effect is very important to determine the geometry in the dimer. The insensitive property of the explosive originates from TATB being driven and oriented by strong electrostatic attraction to form a stable stack structure. Its stability comes from the synergistic effect of dispersion and electrostatic interaction.