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

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 B3PW91-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. (authors)