首页> 外文期刊>The Journal of Chemical Physics >PERTURBATIVE TREATMENT OF TRIPLE EXCITATIONS IN COUPLED-CLUSTER CALCULATIONS OF NUCLEAR MAGNETIC SHIELDING CONSTANTS
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PERTURBATIVE TREATMENT OF TRIPLE EXCITATIONS IN COUPLED-CLUSTER CALCULATIONS OF NUCLEAR MAGNETIC SHIELDING CONSTANTS

机译:核磁屏蔽常数耦合群计算中三重激发的微扰处理

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摘要

A theory for the calculation of nuclear magnetic shielding constants at the coupled-cluster singles and doubles level augmented by a perturbative correction for connected triple excitations (CCSD(T)) has been developed and implemented. The approach, which is based on the gauge-including atomic orbital (CIAO) ansatz, is illustrated by several numerical examples. These include a comparison of CCSD(T) and other highly correlated methods with full configuration interaction for the BH molecule, and a systematic comparison with experiment for HF, H2O, NH3, CH4, N-2, CO, HCN, and F-2. The results demonstrate the importance of triple excitations in establishing quantitative accuracy. Finally, the ability of GIAO-CCSD(T) to make accurate predictions for difficult cases is explored in calculations for formaldehyde (CH2O), diazomethane (CH2NN), and ozone (O-3). (C) 1996 American Institute of Physics. [References: 67]
机译:已经开发并实现了一种理论,该理论用于计算通过对连接的三重激发(CCSD(T))进行扰动校正而增强的耦合簇单双峰水平的核磁屏蔽常数。通过几个数值示例说明了该方法,该方法基于包括轨距的原子轨道(CIAO)ansatz。其中包括将CCSD(T)和其他高度相关的方法与BH分子进行完整配置相互作用的比较,以及与HF,H2O,NH3,CH4,N-2,CO,HCN和F-2的实验进行系统比较。结果证明了三次激发在建立定量精度中的重要性。最后,在计算甲醛(CH2O),重氮甲烷(CH2NN)和臭氧(O-3)的过程中,探索了GIAO-CCSD(T)对困难情况做出准确预测的能力。 (C)1996年美国物理研究所。 [参考:67]

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