Some remarks about a generalized SCF coupling operator open shell theory

✍ Scribed by Ramón Carbó; Ramón Gallifa; Josep M. Riera

• Publisher: Elsevier Science
• Year: 1975
• Tongue: English
• Weight: 741 KB
• Volume: 30
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(75)85494-7

✦ Synopsis

Li and He atomic systems rue studied from the point of view of a general monoconfigurational Hartrec-Fock coupling operator formalism. As a conscquencc, it is found that Lagrange multiplier hermitean cond/tions shouId be fulfilled in those electronic systems where hcrmiticity is not present by symmetry reasons, as in the Li ground state -and the He first excited singlet. An additional condition is also needed when an excited state of the same symmetry and multiplicity of ground state should be calculated, as in He, allowing to apply the variational principIs to the escited state energy functional. Without this condition, the monoconfigurational Hartree-Fock p:ocedurc wiIl lead to unphl ical energies. In semi-empirical calculations, however, the herrnitean condition may be relaxed without provoking appreciable errors. The NOa molecule is analyzed within the CNDO framework to prove this possibility, which simplifies the treatment.