Many‐Electron Theory of Nonclosed‐Shell Atoms and Molecules. I. Orbital Wavefunction and Perturbation Theory

摘要: A theory of electron correlation in nonclosed‐shell states, such as excited states atoms and molecules, triplet free radicals, transient species, is developed. general (multiconfiguration) restricted Hartree—Fock (GRHF) wavefunction taken the starting point. When near degeneracies are not strong enough to cause large orbital charge deformations, Roothaan‐type (RHF) open‐shell theories used. The first‐order Schrodinger equation with RHF zeroth‐order solved. Various processes (near‐degeneracy‐type internal correlations, semi‐internal pair correlations which only one ejected out sea, external closed shells, spin symmetry average polarization effects) obtained a form separated from another. second‐order energy also includes ``cross‐pair effects,'' an phenomenon that need be into account ev...