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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Multilayer Formulation of the Fragment Molecular Orbital Method (FMO)
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Multilayer Formulation of the Fragment Molecular Orbital Method (FMO)

机译：片段分子轨道法（FMO）的多层配方

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The fragment molecular orbital method (FMO) has been generalized to allow for multilayer structure.Fragments are assigned to layers,and each layer can be described with a different basis set and/or level of electron correlation.Interlayer boundaries are treated in the general spirit of the FMO method since they also coincide with some interfragment boundaries.The question of the one- and two-layer FMO accuracy dependence upon the fragmentation scheme is also addressed.The new method has been applied to predict the reaction barrier and the reaction heat for the Diels-Alder reaction with a representative set of reactants based on dividing fragments in two layers.The 6-31G basis set has been used for the active site and the 6-31G,6-31G,3-21G,and STO-3G basis sets have been used for the substituents.Different levels of electron correlation (RHF,B3LYP,and MP2) have been applied to layers in systematic fashion.The one-layer FMO errors in the reaction barrier and the reaction heat were 2.0 kcal/mol or less for all levels applied (RHF,B3LYP,and MP2),relative to full ab initio methods.For the two-layer method the error was found to be several kcal/mol.Benchmark calculations of the activation barrier for the decarboxylation of phenylcyanoacetate by beta-cyclodextrin demonstrated that the two-layer calculations are efficient,being 36 times faster than the regular DFT,as well as accurate,with the error being 1.0 kcal/mol.
机译：碎片分子轨道方法（FMO）已被推广以允许多层结构。将碎片分配给各层，并且可以用不同的基础集和/或电子相关性级别来描述每一层。由于FMO方法也与一些片段间边界相吻合，因此还解决了一层和两层FMO精度依赖于裂解方案的问题。该新方法已用于预测反应的障碍和反应热。 Diels-Alder反应的代表是一组基于两段划分的片段的反应物。6-31G基础集已用于活性位点以及6-31G，6-31G，3-21G和STO-3G基团用于取代基。系统地将不同水平的电子相关性（RHF，B3LYP和MP2）应用于层。反应势垒和反应热中的一层FMO误差为2.0 kc相对于完全从头算法，所施加的所有水平（RHF，B3LYP和MP2）均小于或等于1 kmol / mol。对于两层方法，发现误差为数kcal / mol。 β-环糊精对苯基氰基乙酸酯的脱羧表明，两层计算是有效的，比常规DFT快36倍，并且准确，误差为1.0 kcal / mol。

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