[molpro-user] CASPT2 convergence problem

Werner Győrffy gyorffy at theochem.uni-stuttgart.de
Wed Nov 6 07:22:09 GMT 2013

Dear Yang,

You can try to increase the the number of configurations in the primary 
configuration space by using the PSPACE card. Increase the threshold 
value to, for example, 1 (PSPACE,1). In the primary configuration space, 
the Hamiltonian is constructed and diagonalized explicitly which may 
stabilize your CASPT2 calculations. For further details, see PSPACE in 
the manual.


Werner Gyorffy.

On 11/05/2013 09:02 PM, Yang Yang wrote:
> Hi, Dear Molpro Community,
> I'm trying to solve the lowest 3 excited states with a particular
> symmetry and spin in a CASPT2 calculation. The previous state-averaged
> CASSCF calculation *always* converges successfully. However, only the
> first excited state in the CASPT2 calculation can converge. If I include
> the second or/and third state(s) in a multi-state CASPT2 or solve the
> second/third state individually, then there is no convergence.
> I have tried to use different CASSCF reference states as the initial
> guess, modify the level shift or increase the iteration number. None
> worked so far. Any other things i may try to help the convergence?
> Thanks a lot!
> Sincerely
> yang
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