Re: CCL:TDDFT on G03: negative transition energies

This comment is strongly tied to the Thouless instability condition [see copious work by Paldus and Cizek in the 60's.] Negative eigenvalues were discussed as a direction in which to improve the reference wavefunction, usually the ground state. Rolf Seeger et. al. placed such code in Gxy for HF wave functions, I believe...
 John McKelvey
 T. Daniel Crawford wrote:
 It should be noted that, in the TD-DFT framework (which is closely related
 to RPA), the response matrix cannot technically have negative eigenvalues.
 I would speculate that the eigenvalues reported by the code as negative are
 actually pure imaginary.  This does indicate an "instability" in the
 response matrix, which you could perhaps interpret as a lower-energy state.
 On 6/2/05 1:09 PM, "S.I.Gorelsky" <gorelsky ::>
 I have done some B3lyp TDDFT calculations on some
 transition metal complexes and I have obtained some
 negative excitation energies . Does it make sense or
 it is an error of the code? Has anyone come across the
 same problem?
 This means that what you have got as a reference state in your calculation
 is THE EXCITED STATE, and there is at least one lower-energy electronic
 state (the TRUE ground state) at the given level of theory.
 S. Gorelsky
 Dr S.I. Gorelsky, Department of Chemistry, Stanford University
 Box 155, 333 Campus Drive, Stanford, CA 94305-5080 USA
 Phone: (650) 723-0041. Fax: (650) 723-0852.
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