CCL:G: Calculation absorption spectrum using Gaussian G03

[Serge Gorelsky <gorelsky###gmail.com>]

 Sent to CCL by: Serge Gorelsky [gorelsky]=[gmail.com]
 Negative excitation energies in TD-DFT calculations mean that there
 are lower energy electronic states relative to the "reference"
 electronic state. This is one of the tests to determine whether or not
 the reference state is the true ground state: if there are negative
 excitation energies, the reference state is NOT the ground state.
 On Wed, Dec 22, 2010 at 11:59 AM, Pilar Constanza Suarez
 pcs_3++hotmail.com <owner-chemistry++ccl.net> wrote:
 >
 > Sent to CCL by: "Pilar Constanza Suarez" [pcs_3::hotmail.com]
 > Dear All.
 >
 > We try to calculate the UV-VIS absorption spectra of one gold atom whit
 > multiplicities 1 (ground state),3 y 5 using Gaussian 03 (Geometry
 optimization
 > of these molecules was obtained using b3pw91 method).
 >
 > The simulations to calculate absorption spectrum finished without errors
 but
 > when I checked the output files with AGUI the excitation energy values for
 gold
 > atom with multiplicities 3 and 5 are NEGATIVES.
 >
 > So I would like to know why these values are negatives and what it means?
 >
 > Also what happens if the calculation (UV-VIS absorption spectra) starts
 from an
 > excited open shell state?
 >
 > Thank you.
 >
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 >
 >
 --
 Best regards,
 Â Serge Gorelsky