O'Connor Dana, Bier Imanuel, Hsieh Yun-Ting, Marom Noa
Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States.
Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States.
J Chem Theory Comput. 2022 Jul 12;18(7):4456-4471. doi: 10.1021/acs.jctc.2c00350. Epub 2022 Jun 27.
Molecular crystals of energetic materials (EMs) are denser than typical molecular crystals and are characterized by distinct intermolecular interactions between nitrogen-containing moieties. To assess the performance of dispersion-inclusive density functional theory (DFT) methods, we have compiled a data set of experimental sublimation enthalpies of 31 energetic materials. We evaluate the performance of three methods: the semilocal Perdew-Burke-Ernzerhof (PBE) functional coupled with the pairwise Tkatchenko-Scheffler (TS) dispersion correction, PBE with the many-body dispersion (MBD) method, and the PBE-based hybrid functional (PBE0) with MBD. Zero-point energy contributions and thermal effects are described using the quasi-harmonic approximation (QHA), including explicit treatment of thermal expansion, which we find to be non-negligible for EMs. The lattice energies obtained with PBE0+MBD are the closest to experimental sublimation enthalpies with a mean absolute error of 9.89 kJ/mol. However, the state-of-the-art treatment of vibrational and thermal contributions makes the agreement with experiment worse. Pressure-volume curves are also examined for six representative materials. For pressure-volume curves, all three methods provide reasonable agreement with experimental data with mean absolute relative errors of 3% or less. Most of the intermolecular interactions typical of EMs, namely nitro-amine, nitro-nitro, and nitro-hydrogen interactions, are more sensitive to the choice of the dispersion method than to the choice of the exchange-correlation functional. The exception is π-π stacking interactions, which are also very sensitive to the choice of the functional. Overall, we find that PBE+TS, PBE+MBD, and PBE0+MBD do not perform as well for energetic materials as previously reported for other classes of molecular crystals. This highlights the importance of testing dispersion-inclusive DFT methods for diverse classes of materials and the need for further method development.
含能材料（EMs）的分子晶体比典型分子晶体密度更大，其特征是含氮部分之间存在独特的分子间相互作用。为了评估包含色散的密度泛函理论（DFT）方法的性能，我们编制了一个包含31种含能材料实验升华焓的数据集。我们评估了三种方法的性能：与成对的Tkatchenko-Scheffler（TS）色散校正相结合的半局域Perdew-Burke-Ernzerhof（PBE）泛函、采用多体色散（MBD）方法的PBE以及采用MBD的基于PBE的杂化泛函（PBE0）。零点能量贡献和热效应使用准谐近似（QHA）来描述，包括对热膨胀的显式处理，我们发现这对含能材料来说是不可忽略的。用PBE0 + MBD获得的晶格能最接近实验升华焓，平均绝对误差为9.89 kJ/mol。然而，对振动和热贡献的最新处理使得与实验的一致性变差。还对六种代表性材料的压力-体积曲线进行了研究。对于压力-体积曲线，所有三种方法与实验数据都有合理的一致性，平均绝对相对误差为3%或更小。含能材料中典型的大多数分子间相互作用，即硝基-胺、硝基-硝基和硝基-氢相互作用，对色散方法选择的敏感性高于对交换-相关泛函选择的敏感性。例外情况是π-π堆积相互作用，其对泛函的选择也非常敏感。总体而言，我们发现PBE + TS、PBE + MBD和PBE0 + MBD对含能材料的性能不如之前针对其他类分子晶体所报道的那样好。这突出了针对不同类材料测试包含色散的DFT方法的重要性以及进一步开发方法的必要性。
