Author Topic: Singlet excited state geometry optimization problems  (Read 5450 times)

wiking

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Singlet excited state geometry optimization problems
« on: January 06, 2008, 11:45:17 am »
Hi!
PLEASE HELP!!!
I'm trying to optimize geometry of singlet excited state (using dft=>b3-lyp and bp86=>rpas). After optimization of ground state I call dscf, escf and egrad (without any troubles), but when I call jobex to optimize excited state I met a trouble which I can't cope with. My optimization died without any message error. It usually stopped after several cycles (2-5) at an unconverged gradient.

DIRECT SCF FAILED TO CONVERGE => jobex quits

I call jobex using command: nohup jobex -ex -c 200
What can I do to make my optimizations done?

Thanks in advance!
Marcin

christof.haettig

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Re: Singlet excited state geometry optimization problems
« Reply #1 on: January 07, 2008, 08:36:09 am »
Hi,

you should check why the dscf calculation at the last geometry failed. In particular you should check the
geometry and the orbitals (and their energies). It might be that your system dissociates in S1or that it
relaxes along a path where in the ground state a bond will be broken or some other multireference problem is met...

I'm sorry to say that: but excited state calculations with response methods (TDDFT, but also RPA, CIS, CIS(D), CC response, etc.) rely on an appropriate description of the ground state by the underlying ground state method. If this is not (or in geometry optimization: no longer) the case, they can not (or: no longer)  be used.

Christof