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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Molecular Packing and Molecular Dynamics Study of the Tansferability of a Generalized Nitramine Intermolecular Potential to Non-Nitramine Crystals
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Molecular Packing and Molecular Dynamics Study of the Tansferability of a Generalized Nitramine Intermolecular Potential to Non-Nitramine Crystals

机译：广义硝胺分子间电势对非硝胺晶体的转移性的分子堆积和分子动力学研究

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摘要

We have analyzed the transferability of a previously proposed intermolecular potential for nitramine crystals to reproduce the experimentally determined crystal structures (within the approximation of rigid molecules of 51 nitro compounds. These compounds include different types of acyclic, monocyclic, and polycyclic molecules. It is shown that this potential model accurately reproduces the experimentally determined crystallopgraphic structures and lattice energies for the majority of these crystals. The best agreement with experimental structural and energetic data is obtained when the electrostatic charges have been determined using ab initio methods that include electron correlation effects, namely MP2 and B3LYP. The use of the electrostatic charges calculated at the Hartree-Fock level results in large differences between the predicted and the experimental values of the lattice energies. This difference can be significantly decreased by scaling the electrostatic charges with a general factor without introducing significant variations of the predicted crystallographic parameters. Further testing of the proposed intermolecular potential has been done by performing isothermal-isobaric molecular dynamics (MD) simulations over the temperature range 100-450 K, at atmospheric pressure, for the monoclinic phase of the 2,4,6-trinitrotoluene (TNT) crystal and for the polymorphic phase I of the pentaerythritol tetranitrate (PETN I) crystal. In each case, the results show that throughout the MD simulations the average structures of the crystals maintain the same space group symmetry as the one determined experimentally and there is a good agreement between the calculated crystallographic parameters and the experimental values. The thermal expansion coefficients calculated using the present model indicate an overall anisotropic behavior for both TNT and PETN I, with a thermal isotropy for PETN I along cell directions a and b.
机译：我们已经分析了先前提出的用于硝胺晶体的分子间电位的可转移性，以再现实验确定的晶体结构（在51个硝基化合物的刚性分子附近。这些化合物包括不同类型的无环，单环和多环分子。该势能模型可以准确地再现大多数晶体的实验确定的晶体学结构和晶格能，当使用包括电子相关效应的从头算方法确定静电荷时，可以得到与实验结构和高能数据的最佳一致性。 MP2和B3LYP。使用Hartree-Fock级计算的静电荷会导致晶格能量的预测值和实验值之间存在较大差异，可以通过按比例缩放静电荷来显着减小这种差异。在不引入预测的晶体学参数显着变化的情况下进行。对于2,4,6-三硝基甲苯（TNT）的单斜晶相，通过在100-450 K的温度范围内，大气压下进行等温-等压分子动力学（MD）模拟，已经完成了对提议的分子间电势的测试。季戊四醇四硝酸盐（PETN I）的多晶型I。在每种情况下，结果表明，在整个MD模拟中，晶体的平均结构与实验确定的晶体保持相同的空间群对称性，并且所计算的晶体学参数与实验值之间具有良好的一致性。使用本模型计算出的热膨胀系数表明TNT和PETN I的整体各向异性，而PETN I沿细胞方向a和b具有各向同性。

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