Additions and Corrections - Effect of Electron Correlation on Theoretical Equilibrium Geometries. 2. Comparison of Third-Order Perturbation and Configuration Interaction Results with Experiment

1983 ◽  
Vol 105 (11) ◽  
pp. 3745-3745 ◽  
Author(s):  
Douglas DeFrees ◽  
Krishnan Ragavachari ◽  
H. Schlegel ◽  
John Pople
Keyword(s):  
Configuration Interaction ◽  
Electron Correlation ◽  
Order Perturbation ◽  
Third Order ◽  
Equilibrium Geometries

Correlation Effects of Third-order Perturbation in the Extended Hubbard Model

1989 ◽  
Vol 42 (5) ◽  
pp. 565
Author(s):  
CZ Wei ◽  
HQ Nie ◽  
L Li ◽  
KY Zhang
Keyword(s):  
Hubbard Model ◽  
Electron Correlation ◽  
Spin Correlation ◽  
Order Perturbation ◽  
Atomic Electron ◽  
Nearest Neighbour ◽  
Extended Hubbard Model ◽  
Third Order ◽  
The Third ◽  
Significant Correction

Using the local approach, we have performed a third�order perturbation calculation to investigate the effects of intra-atomic electron correlation and electron and spin correlation between nearest neighbour sites in the extended Hubbard model. We found that significant correction of the third order over the second order results and, in comparison with the results of the third-order perturbation where only the intra-atomic electron correlation is included, the influence of the electron and spin correlation between nearest neighbour sites on the correlation energy is non-negligible.

LOCAL APPROACH TO VARIATIONAL METHOD FOR ELECTRON CORRELATION IN NARROW BAND SYSTEMS

1987 ◽  
Vol 01 (05n06) ◽  
pp. 1311-1320 ◽  
Author(s):  
GUO-ZHU WEI ◽  
HUI-QUAN NIE ◽  
KAI-YI ZHANG ◽  
K.A. CHAO
Keyword(s):  
Electron Correlation ◽  
Narrow Band ◽  
Correlation Effect ◽  
Second Order ◽  
Order Perturbation ◽  
Extended Hubbard Model ◽  
Perturbation Calculation ◽  
Local Approach ◽  
Third Order ◽  
Electron Correlation Effect

Using the local approach, we have performed a third order perturbation calculation to investigate the electron correlation effect in extended Hubbard model with both positive and negative intraatomic and interatomic correlation energies. We found the significant third order correction over the second order terms. Consequently, all published results, especially the phase diagrams which were derived with the second order perturbation calculation are not reliable.

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