Electron configuration interaction

For some systems a single determinant (SCFcalculation) is insufficient to describe the electronic wave function. For example, square cyclobutadiene and twisted ethylene require at least two configurations to describe their ground states. To allow several configurations to be used, a multi-electron configuration interaction technique has been implemented in HyperChem. 

Magnesium requires at least a two-electron configuration-interaction calculation with a frozen ls 2s 2p core. We give a detailed example of a large calculation (Mitroy, 1983) and the results of other calculations to show how well structure calculations can describe spectroscopic data. 

Circular Dichroism Electronic Configuration Interaction Density Functional Theory (DFT), Hartree-Fock (HF), and the Self-consistent Field Force Fields A Brief Introduction Force Fields A General Discussion Geometry Optimization I Geometry Optimization 2 Infrared Data Correlations with Chemical Structure Intensities of Infrared and Raman Bands Magnetic Circular Dichroism of it Systems Molecular Magnetic Properties. 

Circular Dichroism Electronic Configuration Interaction Semiempirical Calculations Molecular Mechanics Conjugated Systems Spectroscopy Computational Methods Structure Determination by Computer-based Spectrum Interpretation Symmetry in Chemistry. 

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