Davidson Correction

\Delta \ E_Q = (1 - a_0^2)(E_{CISD} - E_{HF}) \

E_{CISDTQ} = E_{CISD} + \Delta \ E_Q \

a_0 \

is the coefficient of the Hartree-Fock Wavefunction in the CISD expansion.

E_{CISD} \

and

E_{HF} \

are the energies of the CISD and Hartree-Fock wavefunctions respectively.

\Delta \ E_Q

is an estimate of the correction required to estimate

E_{CISDTQ} \

, the energy of the CISDTQ wavefunction.

REFERENCE

Langhoff, S. R. and Davidson, E. R., ''International Journal of Quantum Chemistry'', 8, 61, (1974)

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