[CPMD-list] problems with TDDFT geometry optimizatioin

[Axel Kohlmeyer]

On 10 Jun 2005, Eneritz Muguruza gonzalez wrote:

eneritz,

you seem to be using a very old development(!) version of CPMD
can you please verify, that the problem persists with the
latest CPMD release. i seem to remember there were some fixes
specifically for geometry optimization with constraints but
also quite a few general bugfixes. i am not an expert for
TDDFT, and didn't really look much further than the first
part of your output, but please understand, that before 
somebody spends some time figuring out what is going wrong, 
you should at least make sure that it has not been fixed since.

regards,
	axel.



EMG> CPMD users,
EMG> 
EMG>    
EMG>        I am doing TDDFT torsion constraint geometry optimization
EMG>  calculations for an isolated molecule. I am calculating the relaxed
EMG>  structures within an excited state at several torsional angles. For the
EMG>  angles 180, 135, 45 and 0 everything goes more or less well, but for
EMG> the twisted tau=90 structure the geometry optimization crashes. At the
EMG> beginning of the geometry optimization the forces and energies go down
EMG>  well, but at a certain step the energy drops drastically (to a value
EMG>  similar to the one in the ground state) while the forces increase very
EMG>  much (1 order of magnitude). Looking at the output file, at this point
EMG>  the 2nd order perturbation energy goes to 0.  
EMG>  
EMG>        Does anybody know why this is happening? Is there some problem
EMG> with the code? How can it be solved?
EMG> 
EMG>  I would really appreciate if somebody could give me a hint. Thanks!
EMG>  
EMG>    
EMG>                       Eneritz
EMG>  
EMG>  
EMG>  I attach the output file so you can have a look.      
EMG> 

-- 

=======================================================================
Dr. Axel Kohlmeyer   e-mail: axel.kohlmeyer at theochem.ruhr-uni-bochum.de
Lehrstuhl fuer Theoretische Chemie          Phone: ++49 (0)234/32-26673
Ruhr-Universitaet Bochum - NC 03/53         Fax:   ++49 (0)234/32-14045
D-44780 Bochum  http://www.theochem.ruhr-uni-bochum.de/~axel.kohlmeyer/
=======================================================================
If you make something idiot-proof, the universe creates a better idiot.