CI

CI - Electron Correlation - Configuration Interaction...

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Electron Correlation - Configuration Interaction Because electrons are negatively charged, electrons like to avoid each other. When one electron moves the positions of the other electrons in the molecule adjust to minimize electron-electron repulsion. Therefore, the motions of the electrons are not independent. In other words, the motion of the electrons is correlated. The current best method for adjusting the molecular wavefunctions for electron correlation is called configuration interaction, or CI for short. CI calculations allow the ground state of a molecule to mix with excited states of the molecule. For example for the H 2 molecule, the ground state configuration and several excited states are diagrammed below. σ σ * HH 1s 1s E σ σ * 1s 1s E σ σ * 1s 1s E Ground State Single Excitation Double Excitation In CI calculations the ground state wavefunction is allowed to be a combination of all of the possible excited states: E gs = 0.9987* σ σ * 1s 1s E + 0.0518* σ σ * 1s 1s E
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This document was uploaded on 02/22/2012.

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