[molpro-user] Unclear problem in EOM-CCSD calculations: "small eigenvalue of S-eff matrix ... This can lead to convergence problems!"
tania at tiger.chem.uw.edu.pl
Wed Jun 7 17:20:34 CEST 2017
This message can signify near-linear dependencies in the small space in the
Davidson procedure. One can try to a) increase the quality of the integrals (for
the case when this dependence is caused by numerical noise of orbitals and CCSD
amplitudes - note that if CCSD is not a final step, a bit more accurate
T1+T2 amplitudes are often required); b) try to play with Davidson options, e.g.
Another issue is a high energy of the virtual orbital. I presume you want to
obtain some high-lying states, what often means that there is a large density of
states having a significant component of the excitation to this orbital and
then the procedure will jump from one state to another and back (or to yet
another state). In this case sometimes it helps if you ask for more states (but
only sometimes). In general finding high states is a difficult no-black-box
task, unfortunately :-(
On Tue, 6 Jun 2017, Evgeniy Gromov wrote:
> I encountered some unclear problem when doing EOM-CCSD calculations
> for an Ir complex. All steps till EOM went fine, but in EOM I get the
> following warning:
> The smallest eigenvalue of S-eff matrix 0.8656157915E-13
> This can lead to convergence problems!
> and two of the five roots do not seem to have converged; there is
> no "Converged" message for them after 50 iterations.
> I wonder what this could be caused by? Could it be due to a very high
> in energy (63.5 hartree) virtual orbital?
> Best regards,
> Dr. Evgeniy Gromov
> Theoretische Chemie
> Physikalisch-Chemisches Institut
> Im Neuenheimer Feld 229
> D-69120 Heidelberg
> Telefon: +49/(0)6221/545213
> Fax: +49/(0)6221/545221
> E-mail: evgeniy.gromov at pci.uni-heidelberg.de
> Molpro-user mailing list
> Molpro-user at molpro.net
Dr. Tatiana Korona http://tiger.chem.uw.edu.pl/staff/tania/index.html
Quantum Chemistry Laboratory, University of Warsaw, Pasteura 1, PL-02-093 Warsaw, POLAND
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