[molpro-user] UCCSD(T) calculation with DHF-QZVP-2C set does not converge for a Cs atom

sasha medvedev vinsanity305 at mail.ru
Wed Apr 23 21:02:16 BST 2014

 Hello, molpro users and developers.

I met a rather strange result: 
uccsd(t) calculation for a Cs atom did not converge,
when I used dhf-qzvp-2c basis set. 

So, the ending of the output file was as following:

? Error
 ? No convergence. This error exit can be avoided using the NOCHECK option
 ? The problem occurs in ccsd

Here is the code (I also attached the appropriate input file to this mail):

I should note, that the dhf-qzvp-1c set converges in such calculation (you can run the attached input file - it contains both sets).
And, by the way, the difference between -1c and -2c set is only in two 
p-functions, which are added to take into account spin-orbit effects.
Of course, I see that the result depends on global thresholds [so, calculations with dhf-qzvp-2c set converge for bigger thresholds; 
for instance with:  gthresh,energy=1.d-6,orbital=1.d-5,coeff=1.d-5 ]. 
But it still seems to be strange, that almost the same basis set doesn't converge in the 
same routine.

I use molpro2010, so I take dhf basis sets here:  http://www.cosmologic.de/basis-sets/basissets.php

Alexander Medvedev,
student of the 5th course,
MSU, Chemistry Department,
Chair of laser chemistry
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