Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, Tennessee 37996, USA.
Langmuir. 2010 Apr 20;26(8):5942-50. doi: 10.1021/la9039013.
Quantum mechanical (QM) calculations, classical grand canonical Monte Carlo (GCMC) simulations, and classical molecular dynamics (MD) simulations are performed to test the effect of charge distribution on hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) adsorption and diffusion in IRMOF-10. Several different methods for mapping QM electron distributions onto atomic point charges are explored, including the electrostatic potential (ESP) method, Mulliken population analysis, Lowdin population analysis, and natural bond orbital analysis. Classical GCMC and MD simulations of RDX in IRMOF-10 are performed using 15 combinations of charge sources of RDX and IRMOF-10. As the charge distributions vary, interaction potential energies, the adsorption loading, and the self-diffusivities are significantly different. None of the 15 combinations are able to quantitatively capture the dependence of the energy of adsorption on local configuration of RDX as observed in the QM calculations. We observe changes in the charge distributions of RDX and IRMOF-10 with the introduction of an RDX molecule into the cage. We also observe a large dispersion contribution to the interaction energy from QM calculations that is not reproduced in the classical simulations, indicating that the source of discrepancy may not lie exclusively with the assignment of charges.
采用量子力学（QM）计算、经典巨正则蒙特卡罗（GCMC）模拟和经典分子动力学（MD）模拟，研究了电荷分布对六氢-1,3,5-三硝基-1,3,5-三嗪（RDX）在 IRMOF-10 中吸附和扩散的影响。探索了几种将 QM 电子分布映射到原子点电荷的不同方法，包括静电势（ESP）方法、Mulliken 布居分析、Lowdin 布居分析和自然键轨道分析。使用 RDX 和 IRMOF-10 的 15 种电荷源组合，对 RDX 在 IRMOF-10 中的经典 GCMC 和 MD 模拟进行了研究。随着电荷分布的变化，相互作用势能、吸附负载和自扩散系数有显著差异。这 15 种组合都无法定量捕获 QM 计算中观察到的 RDX 局部构型对吸附能的依赖性。我们观察到在笼中引入 RDX 分子后，RDX 和 IRMOF-10 的电荷分布发生了变化。我们还观察到 QM 计算中相互作用能的大色散贡献在经典模拟中无法重现，这表明差异的来源可能不仅仅在于电荷的分配。
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