The Kohn Sham matrix is not 100% occupied
Claudio
marg... at gmail.com
Mon Nov 16 16:14:18 CET 2009
Thanks Manuel, I just read the paper.
I will try some of this and will report back.
Cheers,
Claudio
On Nov 16, 8:13 am, mguidon <manuel... at gmail.com> wrote:
> Hi Claudio.
>
> There are several issues that could cause troubles in a periodic HFX
> calculation:
>
> 1. Always use the truncated Coulomb operator, otherwise your results
> might converge to an unphysical wavefunction (i.e. total energies a
> far lower than what you would expect)
> 2. The sparsity-patterns of the Fock- and Kohn-Sham matrice are not
> the same. This issue can be solved by putting EPS_PGF_ORB to 1.0E-32
> or similar. (But usually, a 90 % occupied Kohn-Sham matrix is good
> enough, especially when you apply the truncated potential)
> 3. By putting a threshold on all the integrals (EPS_SCHWARZ) you
> introduce some random errors of the same order. As a rule of thumb,
> eps_schwarz should be roughly equal to the inverse square of the
> condition number of the overlap matrix. For example: If the condition
> number of the overlap matrix is 1.0E4, then you should put eps_schwarz
> to 1.0E-8 (but this is a worst case estimate!) Keep in mind, that the
> amount of work roughly doubles by decreasing eps_schwarz by one order
> of magnitude. It might be better to decrease the condition number of
> the overlap matrix by choosing a less diffuse basis set.
> 4. Always add the keyword EPS_STORAGE_SCALING 1.0E-1 in order to avoid
> suppress noise in the compression/decompression routines.
>
> For more details see
>
> J. Chem. Theory Comput., 2009, 5 (11), pp 3010-3021
>
> Hope that helps
>
> Manuel
>
> On Nov 16, 1:56 pm, Claudio <marg... at gmail.com> wrote:
>
>
>
> > Dear all, when I try to run a periodic HF calculation or a mixed HF
> > DFT run (b3lyp) for example. I always get
>
> > *** 06:49:15 WARNING in
> > hfx_energy_potential:integrate_four_center ***
> > *** err=-300 The Kohn Sham matrix is not 100% occupied. This may
> > result ***
> > *** in uncorrect Hartree-Fock results. Try to decrease EPS_PGF_ORB in
> > the ***
> > *** QS
> > section.
> > ***
>
> > Same system converges without problem without HF using for example
> > PBE. I tried decreasing EPS_PGF_ORB and EPS_DEFAULT without much
> > success. I also tried decreasing basis set size. I am not using a
> > truncated potential.
>
> > Is this warning relevant? I am having a very hard time converging the
> > b3lyp calculation.
>
> > Thanks,
> > Claudio
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