A refined cluster-in-molecule local correlation approach for predicting the relative energies of large systems.
A refined cluster-in-molecule local correlation approach for predicting the relative energies of large systems.
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DOI：
10.1039/c2cp23916g
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发表时间：
2012-05
期刊：
影响因子：
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通讯作者：
Wei Li;Yang Guo;Shuhua Li
中科院分区：
文献类型：
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作者：
Wei Li;Yang Guo;Shuhua Li
提出了一种用于大分子局域关联计算的精细分子团簇（CIM）方法。本文提出了两种改进CIM方法的新策略：（1）考虑了在CIM方法中被忽略的一些中程电子相关能。(2)一个简单得多的过程，只使用一个距离阈值被用来构建各种集群。为了尽可能地覆盖中程关联效应，除了单原子团簇外，还建立了一些双原子团簇。我们在二阶微扰理论（MP2）水平上的测试计算表明，改进的CIM方法可以恢复约99.9%的常规MP2相关能量使用适当的距离阈值。本CIM方法的准确性能够提供中等大小系统的可靠相对能量，例如具有10个残基的聚丙氨酸和具有50个水分子的水分子。对于具有多达30个残基的聚丙氨酸，我们已经证明了CIM-MP2计算的计算成本随着分子大小线性增加，但是对于大型系统，所需的存储器和磁盘空间不需要增加。用改进的CIM方法计算了类冰（H（2）O）（96）团簇的相对能量（2400个基函数）和双螺旋折叠体的二聚化能（2330个基函数）.本CIM方法有望成为描述大系统相对能量的实用局部相关方法。
A refined cluster-in-molecule (CIM) method for local correlation calculations of large molecules is presented. In the present work, two new strategies are introduced to further improve the CIM approach: (1) Some medium-range electron correlation energies, which are neglected in the previous CIM approach, are taken into account. (2) A much simpler procedure using only a distance threshold is used to construct various clusters. To cover the medium-range correlation effect as much as possible, some two-atom-centered clusters are built, in addition to one-atom-centered clusters. Our test calculations at the second order perturbation theory (MP2) level show that the refined CIM method can recover about 99.9% of the conventional MP2 correlation energy using an appropriate distance threshold. The accuracy of the present CIM method is capable of providing reliable relative energies of medium-sized systems such as polyalanines with 10 residues, and water molecules with 50 water molecules. For polyalanines with up to 30 residues, we have demonstrated that the computational cost of the CIM-MP2 calculation increases linearly with the molecular size, but the required memory and disc-space do not need to increase for large systems. The improved CIM method has been used to compute the relative energy of ice-like (H(2)O)(96) clusters (with 2400 basis functions) and to predict the dimerization energy of a double-helical foldamer (with 2330 basis functions). The present CIM method is expected to be a practical local correlation method for describing the relative energies of large systems.