Multiconfigurational perturbation theory
This thesis develops a Rayleigh-Schroedinger perturbation theory applicable to multiconfigurational wave functions. This perturbation theory effectively approximates the direct diagonalization approach by constructing, for a chosen reference space, an appropriate zeroth-order Hamiltonian and associated perturbative potential. The simplified nature of the zeroth-order Hamiltonian leads to higher computational efficiency relative to direct diagonalization, thus allowing for the correlation of larger systems. Most importantly, the convergence of the perturbation series is far superior to the traditional Hartree-Fock based perturbation theories when the Hartree-Fock reference is an inadequate zeroth-order approximation. This multiconfigurational perturbation theory is applied up to third-order to the determination of the potential surfaces of molecules with single and multiple bonds. In addition, the determination of energy differences between different molecular and atomic electronic states is studied. The use of a multiconfigurational reference wave function is shown to be essential in many cases for obtaining physically meaningful low-order corrections to the reference space.
- Research Organization:
- Pennsylvania Univ., Philadelphia, PA (United States)
- OSTI ID:
- 7013746
- Country of Publication:
- United States
- Language:
- English
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