Subject: ROHF orbital energies in G94: summary

From: Konstantin Momot <[email-masked]>
Date: Mon, 24 Mar 1997 13:48:20 +42000

Dear List members,

several days ago, I asked a question about the meaning of energy 
eigenvalues in ROHF.  Drs. P.Th. van Duijen and J.C. Stephens replied, my 
thanks to both of them.  

Briefly, the problem was that ROHF eigenvalues didn't have anything to do 
with IPs even for hydrogen atom.  The problem is a fundamental one, 
rather than G94-specific.  It also does not have anything to do with the 
half-electron method. The problem exists for "doubly-occupied" as well as 
"singly-occupied" orbitals of the ROHF solution.  Strictly speaking, 
neither type can be treated by Koopmans theorem, although "the energies 
of the closed shell orbitals" are numerically close to the corresponding 
ionization potentials.  

The following two papers provide a good discussion of the problem's 
origins:

1.   C.C.J.Roothaan.  Rev. Mod. Phys. 32 (1960) p.179.
2.   Dodds & McWeeny. Chem. Phys. Lett. 13 (1972) p.9.

--

Konstantin Momot

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http://aruba.ccit.arizona.edu/     | and the worst are filled 
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