SUPERPOSITION OF CONFUGURATIONS AND NATURAL SPIN ORBITALS. APPLICATIONS TO THE HE PROBLEM.
UPPSALA UNIV (SWEDEN) QUANTUM CHEMISTRY GROUP
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The method of superposition of configurations is examined in its application to the helium atom in two cases a 21 x 21 matrix including all configurations up to 6s2, and a 20 x 20 matrix with all configurations up to the 4-quantum level, including angular terms. An analysis of the results suggests that inner orbitals may be better represented by pure exponentials than by Hartree-Fock orbitals whenever additional correlational degrees of freedom are permitted. Expressed in approximate natural spin orbital from, the wave function is almost invariant to choice of basis set, provided that the latter is reasonably chosen. In particular, the necessity of including continuum terms along with the discrete hydrogen-like set is demonstrated. Author
- Atomic and Molecular Physics and Spectroscopy
- Quantum Theory and Relativity