Unreasonable Norm in direct CCSD calculation
Benoit Oswald Stanislas BRAIDA
Benoit.Braida at lcp.u-psud.fr
Tue Nov 7 17:02:39 GMT 2000
>Hello Molpro-Users,
>
>I am attempting a 380bf C1 CCSD/avqz SP. I don't have enough disk
>space for a conventional run so I have attempted to use the integral
>direct code in Molpro2000.1.
>
>The SCF runs as expected but the CCSD stops with:
>
>
> ITER. NORM CORR.ENERGY TOTAL ENERGY ENERGY CHANGE DEN1
> VAR(S) VAR(P) DIIS TIME
> 1 1.21231612 -0.79682143 -227.39947808 0.02337258 -0.02968085
> 0.10D-01 0.56D-02 0 0 20369.79
> 2 22.96434217 -0.82003054 -227.42268720 -0.02320911
>-1086.37070545
> 0.22D-03 0.22D+02 0 0 40445.27
>
> UNREASONABLE NORM. CALCULATION STOPPED
>
>Does anyone have general suggestions on how this problem can be avoided.
>
>Thanks in anticipation,
>
>Tony Scott
>______________________________________________________________________________
You face this problem when in the calculation the denominator (DEN1)
become to large, and it is generaly due to the external pairs. You
should try the keyword "shift", which by shifting the value of the
denominator for pairs will give you a better damped calculation.
Try for instance the following input :
ccsd(t)
shift,1
If it doesn't work, try to increase the shift value. Anyway, have a
look to the T1diagnostic at the end of your calculation, because this
kind of error is often the sign of a deeper problem in the CCSD
calculation (mutideterminantal case...).
Benoit BRAIDA
Laboratoire de chimie physique
Groupe de chimie theorique
Universite Paris-Sud, Batiment 490
91405 ORSAY CEDEX
FRANCE
Tel : 33-1-69-15-61-91
Fax : 33-1-69-15-44-47
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