Multilayer formulation of the fragment molecular orbital method (FMO)
Multilayer formulation of the fragment molecular orbital method (FMO)
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DOI：
10.1021/jp047186z
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发表时间：
2005-03-24
影响因子：
2.9
通讯作者：
Kitaura, K
中科院分区：
文献类型：
--
作者：
Fedorov, DG;Ishida, T;Kitaura, K
碎片分子轨道方法(FMO)已被推广到考虑多层结构。碎片被分配到层，并且每一层可以用不同的基组和/或电子相关水平来描述。层间边界是按照FMO方法的一般精神来处理的，因为它们也与一些碎片间边界重合。还讨论了一层和两层FMO精度依赖于分段方案的问题。用这种新方法对Diels-Alder反应的势垒和反应热进行了预测，得到了一组具有代表性的反应物。活性中心采用6-31G*基组，取代基采用6-31G*、6-31G、3-21G和STO-3G基组。不同水平的电子关联(RHF、B3LYP和MP2)已经以系统的方式应用于各层。与全从头计算方法相比，对于所有应用的水平(RHF、B3LYP和MP2)，反应势垒和反应热中的单层FMO误差为2.0千卡/摩尔或更小。对于两层法，误差为几千卡/摩尔。用β-环糊精对苯氰乙酸酯脱羧基的活化势垒进行了基准计算，结果表明，两层法计算速度快36倍，计算精度高，误差为1.0kcal/mol。
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.