Cybulski Sławomir M, Seversen Christopher E
Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA.
J Chem Phys. 2005 Jan 1;122(1):14117. doi: 10.1063/1.1829044.
The results of calculations employing twelve different combinations of exchange and correlation functionals are compared with results of ab initio calculations for two different configurations of the water dimer and three different configurations of the thymine-adenine complex. None of the density functional theory (DFT) treatments could properly reproduce the results of coupled-cluster calculations for all configurations examined. The DFT approaches perform well when the interaction energy is dominated by the electrostatic component and the dispersion energy is less important. Two mechanisms that compensate for the missing dispersion component were identified. The first one is the decrease of the magnitude of the intermolecular exchange-repulsion and the second one is the increase of the magnitude of the attractive deformation energy. For some functionals both effects are observed together, but for some other ones only the second effect occurs. The three correlation functionals that were examined were found to make only very small contributions to the deformation energy. The examination of angular and distance dependence of the interactions shows that the currently available DFT approaches are not suitable for developing intermolecular potential energy surfaces. They could however be used to find global minima on potential energy surfaces governed by intermolecular electrostatic interactions. Additional single point ab initio calculations are recommended as the means of validating optimized structures.
将采用12种不同交换关联泛函组合的计算结果，与水二聚体两种不同构型以及胸腺嘧啶 - 腺嘌呤复合物三种不同构型的从头算结果进行了比较。在所研究的所有构型中，没有一种密度泛函理论（DFT）处理方法能够正确重现耦合簇计算的结果。当相互作用能主要由静电成分主导且色散能不太重要时，DFT方法表现良好。确定了两种补偿缺失色散成分的机制。第一种是分子间交换排斥力大小的降低，第二种是吸引变形能大小的增加。对于某些泛函，两种效应同时出现，但对于其他一些泛函，只出现第二种效应。研究发现，所研究的三种关联泛函对变形能的贡献非常小。对相互作用的角度和距离依赖性的研究表明，目前可用的DFT方法不适用于开发分子间势能面。然而，它们可用于在由分子间静电相互作用主导的势能面上找到全局最小值。建议进行额外的单点从头算计算，作为验证优化结构的手段。
