Full configuration interaction benchmarking of coupled-cluster models for the lowest singlet energy surfaces of N2
Full configuration interaction benchmarking of coupled-cluster models for the lowest singlet energy surfaces of N2
复制标题
N2 最低单线态能量面耦合团簇模型的全构型相互作用基准测试
DOI：
--
复制
发表时间：
2000
期刊：
影响因子：
--
通讯作者：
O. Christiansen
中科院分区：
文献类型：
--
作者：
H. Larsen;J. Olsen;P. Jørgensen;O. Christiansen
用全组态相互作用（FCI）和耦合团簇响应计算研究了N2分子X1 g+，a1 g，a′ 1 u−，w1 Δu，c3 1 u和B 1 u态的势能曲线. 平衡键长，绝热激发能，和谐波频率已获得与耦合簇单模型（CCS），一个近似的耦合簇单和双模型（CC 2），耦合簇单和双模型（CCSD），和一个近似的耦合簇单，双，和三重模型（CC 3），并随后与FCI的结果进行比较。讨论了耦合团簇模型的弱特征和强特征。总体而言，在层级CCS-CC 2-CCSD-CC 3中获得了对FCI的改进。CC 3始终优于CCSD，并且对于所有考虑的光谱常数，CC 3提供了优异的结果。还给出了CC 3模型失败的例子。将非迭代三元组模型CCSDR（3）与迭代三元组模型CC 3和FCI进行比较。CCSDR（3）恢复了CC 3关联贡献的大部分，因此是CC 3模型的廉价替代方案.在全组态相互作用（FCI）和耦合团簇响应计算中，我们研究了N2的X1 g+，a1 g，a′ 1 u-，w1 Δu，c3 1 u和B 1 u态的势能曲线. 平衡键长，绝热激发能，和谐波频率已获得与耦合簇单模型（CCS），一个近似的耦合簇单和双模型（CC 2），耦合簇单和双模型（CCSD），和一个近似的耦合簇单，双，和三重模型（CC 3），并随后与FCI的结果进行比较。讨论了耦合团簇模型的弱特征和强特征。总体而言，在层级CCS-CC 2-CCSD-CC 3中获得了对FCI的改进。CC 3始终优于CCSD，并且对于所有考虑的光谱常数，CC 3提供了优异的结果。还给出了CC 3模型失败的例子。将非迭代三重模型CCSDR（3）与迭代三重模型进行了比较。
The potential-energy curves for the X 1Σg+, a 1Πg, a′ 1Σu−, w 1Δu, c3 1Πu, and b 1Πu states of N2 have been investigated in full configuration interaction (FCI) and coupled-cluster response calculations. The equilibrium bond lengths, adiabatic excitation energies, and harmonic frequencies have been obtained with the coupled-cluster singles model (CCS), an approximate coupled-cluster singles and doubles model (CC2), the coupled-cluster singles and doubles model (CCSD), and an approximate coupled-cluster singles, doubles, and triples model (CC3), and subsequently compared to FCI results. The weak and strong features of the coupled-cluster models are discussed and illustrated. Overall, improvements towards FCI are obtained in the hierarchy CCS–CC2–CCSD–CC3. CC3 is always consistently better than CCSD, and for all the considered spectroscopic constants CC3 provides excellent results. Examples where the CC3 model fails are also given. The noniterative triples model, CCSDR(3), is compared to the iterative triples models CC3 and FCI. CCSDR(3) recovers the major part of the CC3 correlation contribution and is thus a cheap alternative to the CC3 model.The potential-energy curves for the X 1Σg+, a 1Πg, a′ 1Σu−, w 1Δu, c3 1Πu, and b 1Πu states of N2 have been investigated in full configuration interaction (FCI) and coupled-cluster response calculations. The equilibrium bond lengths, adiabatic excitation energies, and harmonic frequencies have been obtained with the coupled-cluster singles model (CCS), an approximate coupled-cluster singles and doubles model (CC2), the coupled-cluster singles and doubles model (CCSD), and an approximate coupled-cluster singles, doubles, and triples model (CC3), and subsequently compared to FCI results. The weak and strong features of the coupled-cluster models are discussed and illustrated. Overall, improvements towards FCI are obtained in the hierarchy CCS–CC2–CCSD–CC3. CC3 is always consistently better than CCSD, and for all the considered spectroscopic constants CC3 provides excellent results. Examples where the CC3 model fails are also given. The noniterative triples model, CCSDR(3), is compared to the iterative tripl...