| Moller-plesset Perturbation Theory |
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Information AboutMoller-plesset Perturbation Theory |
| CATEGORIES ABOUT MøLLER-PLESSET PERTURBATION THEORY | |
| quantum chemistry | |
| computational chemistry | |
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The unperturbed Hartree-Fock Hamiltonian operator is extended by adding a small perturbation : :, where λ is an arbitrary parameter. If the perturbation is sufficiently small, then the resulting wavefunction and energy can be expressed as a Power Series in λ: :, :. Substitution of these series into the time-independent Schrödinger Equation gives a new equation: :. The solution of this equation to zero order gives an energy which is the sum of the orbital energies for the electrons. Solution to first order (''n'' = 1) corrects this energy and gives the Hartree-Fock energy and wave function. To go beyond the Hartree-Fock treatment it is necessary to go beyond first order. Second (MP2), third (MP3), and fourth (MP4) order Møller-Plesset calculations are standard levels used in calculating small systems and are implemented in many computational chemistry codes. Higher level MP level calculations are possible in some code, however, they are rarely used. Systematic studies of MP perturbation theory have shown that it is not a convergent theory at high orders. The convergence properties can be slow, rapid, oscillatory, regular or highly erratic, depending on the precise chemical system or basis set.1 SEE ALSO REFERENCES |
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