Application
Davidson correction is very popular due to its low computational cost. The correction improves contribution of electron correlation to the energy. The size-consistency and size-extensivity problems of truncated CI are alleviated but still exist. In small molecules, accuracy of the corrected energies can be similar to results from coupled cluster theory calculations.
Davidson correction does not give information about wave function. Therefore it cannot be used to correct wave-function-dependent quantities such as dipole moment, charge density and vibronic couplings. Analytical gradients for Davidson corrections are in general not available in quantum chemistry programs.
As with other perturbative approaches, Davidson correction is not reliable when the electronic structure of CISD and the reference Hartree-Fock wave functions are significantly different. The correction is invalid, when is not close to 1. This happens when multi-reference character is significant or when CISD is used to calculate a state that is not the reference state, for example, an excited state or a state with different spin multiplicity.
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