Kohn-Sham orbitals for many-body perturbation theory and CI

✍ Scribed by Markus Warken

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 541 KB
• Volume: 237
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(95)00306-o

✦ Synopsis

Although the physical significance of Kohn-Sham orbitals is only given by the ground state density of the Kohn-Sham quasi-particle system they nevertheless form a single-particle system, which may serve as a basis for perturbation theory or variational methods. Rayleigh-SchrSdinger perturbation series for some molecular test cases, taking different Kohn-Sham quasi-particle systems as zeroth order, are examined in comparision to M¢ller-Plesset perturbation theory. Particular emphasis is given to the convergence properties of the series. The latter is most important regarding recent Ans~itze for improving modem density functionals by perturbative methods. We find that these Kohn-Sham based perturbation series are in general divergent. Also, Kohn-Sham orbital based multi-reference CI calculations are performed with emphasis on excited states as Hartree-Fock orbitals generally provide a poor description of excited states.