Frozen natural orbital coupled-cluster theory: forces and application to decomposition of nitroethane.
Frozen natural orbital coupled-cluster theory: forces and application to decomposition of nitroethane.
复制标题
冻结自然轨道耦合团簇理论：力及其在硝基乙烷分解中的应用。
DOI：
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发表时间：
2008
影响因子：
4.4
通讯作者：
R. Bartlett
中科院分区：
文献类型：
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作者：
Andrew G. Taube;R. Bartlett
冻结自然轨道(FNO)耦合团簇方法将耦合团簇(CC)的计算速度提高了一个数量级，并且在势能面上没有相应的误差。该方法允许将相关计算的虚拟空间减少约一半，从而显著减少执行耦合集群(CC)计算所花费的时间。本文报道了FNO-CC的解析梯度的推导和实现，包括非正则和半正则扰动轨道的所有轨道弛豫。这些导数为CC密度矩阵引入了几个新的轨道弛豫贡献。将FNO-CCSD(T)和FNO-LambdaCCSD(T)应用于一组平衡结构的测试，验证了这些方法能够准确地再现几何形状和振动频率以及能量。用CCSD(T)和LambdaCCSD(T)对硝基乙烷的几种分解途径进行了研究，发现与B3LYP6-311+G(3df，2p)相比，在cc-pVTZ的基础上，60%的FNO虚拟轨道与CCSD(T)在5kcalol数量级上存在差异，过渡态能量也发生了重新排序.
The frozen natural orbital (FNO) coupled-cluster method increases the speed of coupled-cluster (CC) calculations by an order of magnitude with no consequential error along a potential energy surface. This method allows the virtual space of a correlated calculation to be reduced by about half, significantly reducing the time spent performing the coupled-cluster (CC) calculation. This paper reports the derivation and implementation of analytical gradients for FNO-CC, including all orbital relaxation for both noncanonical and semicanonical perturbed orbitals. These derivatives introduce several new orbital relaxation contributions to the CC density matrices. FNO-CCSD(T) and FNO-LambdaCCSD(T) are applied to a test set of equilibrium structures, verifying that these methods are capable of reproducing geometries and vibrational frequencies accurately, as well as energies. Several decomposition pathways of nitroethane are investigated using CCSD(T) and LambdaCCSD(T) with 60% of the FNO virtual orbitals in a cc-pVTZ basis, and find differences on the order of 5 kcalmol with reordering of the transition state energies when compared to B3LYP 6-311 + G(3df, 2p).