Liu Haitao, Chen Peng, Huang Xin, Wei Xianfeng
School of National Defense & Nuclear Science and Technology, Southwest University of Science and Technology, Mianyang, 621010, People's Republic of China.
Institute of Chemical Materials, China Academy of Engineering Physics (CAEP), Mianyang, 621900, People's Republic of China.
J Mol Model. 2024 Feb 26;30(3):84. doi: 10.1007/s00894-024-05877-5.
The in-depth understanding about the stability of chemical bonds in energetic compounds plays a central role for molecular design and safety-related evaluations. Most energetic compounds contain nitro as explosophores, and nitro cleavage is fundamental for thermal and mechanical stability. However, the quantum chemistry approach to accurately predict energy and temperature properties related to bond stability is challenging, due to the tradeoff between computational costs and deviations. Herein, the bond orders are proposed as accurate and computational-cost efficient descriptors for predicting the chemical bond stability and thermal-resistant properties. The intrinsic bond strength index (IBSI) demonstrates the best prediction for experimental homolytic bond dissociation energies (R > 0.996), which is on par with the results from high-precision quantum chemistry methods. The effects from bond connectivity and steric hindrance hierarchy were analyzed to reveal underlying mechanisms. Additionally, the IBSI descriptors are successfully applied to predict the thermal decomposition temperatures of 24 heat-resistant energetic compounds (R = 0.995), thus validating the effectiveness for the prediction and interpretation of chemical bond stability in energetic compounds via a physical organic approach.
All DFT calculations were performed with Gaussian 09 software. To investigate the dependence of the method on functionals and basis sets, 9 DFT methods were considered (B3LYP/6-31G(d,p), B3LYP/6-311G(d,p), B3LYP/def2-TZVP, M062X/6-31G(d,p), M062X/6-311G(d,p), M062X/def2-TZVP, ωB97XD/6-31G(d,p), ωB97XD/6-311G(d,p), and ωB97XD/def2-TZVP). The bond order descriptors LBO and IBSI are obtained through the bond order analysis module in the Multiwfn software.
深入了解含能化合物中化学键的稳定性对于分子设计和安全相关评估起着核心作用。大多数含能化合物含有硝基作为爆炸基团，硝基裂解对于热稳定性和机械稳定性至关重要。然而，由于计算成本和偏差之间的权衡，采用量子化学方法准确预测与键稳定性相关的能量和温度性质具有挑战性。在此，提出键级作为预测化学键稳定性和耐热性能的准确且计算成本高效的描述符。固有键强度指数（IBSI）对实验均裂键解离能的预测效果最佳（R > 0.996），与高精度量子化学方法的结果相当。分析了键连接性和空间位阻层次的影响以揭示潜在机制。此外，IBSI描述符成功应用于预测24种耐热含能化合物的热分解温度（R = 0.995），从而通过物理有机方法验证了其对含能化合物中化学键稳定性预测和解释的有效性。
所有密度泛函理论（DFT）计算均使用高斯09软件进行。为研究方法对泛函和基组的依赖性，考虑了9种DFT方法（B3LYP/6 - 31G(d,p)、B3LYP/6 - 311G(d,p)、B3LYP/def2 - TZVP、M062X/6 - 31G(d,p)、M062X/6 - 311G(d,p)、M062X/def2 - TZVP、ωB97XD/6 - 31G(d,p)、ωB97XD/6 - 311G(d,p)和ωB97XD/def2 - TZVP）。键级描述符LBO和IBSI通过Multiwfn软件中的键级分析模块获得。
