[Wien] :WARNING you might have inconsistent Forces/Energies
Peter Blaha
pblaha at theochem.tuwien.ac.at
Mon Feb 18 08:23:02 CET 2008
I guess it was mentioned several times (also in the UG):
PORT minimizes the ENERGY, using the forces as guidance how to move the
atoms. In particular for small forces and flat potential-surfaces, you
could have inconsistencies between forces and :ENE; i.e. your minimum of
:ENE does NOT correspond to :FOR = 0 (for various reasons, often simply
because the scf-cycle was not fully converged, k-mesh, RKmax,....).
PORT is on the one hand VERY efficient; on the other hand it may get
completely confused when you have a SINGLE not well converged scf-cycle
in the minimization.
Sometimes it helps to repeat min_lapw, because the removes the
"minimization-history", sometimes it is better to proceed with NEW1, but
check if not only the forces go to smaller values, but also :ENE
decreases. Otherwise you have some problems (at least at that level of
accuracy), and may need other compüutational parameters or sphere sizes!
Ravindran Ponniah schrieb:
>
> Dear All,
>
> I have made additional calculations now and found that more than 10% of
> the cases I have problem to relax atom positions using PORT option. This
> can not be changed by various computational parameters I have tried (see
> my previous email). If one change from PORT to NEW1 for the troubled cases
> one can able to optimize atom positions with wien2k.
>
> It appears that PORT is not an efficient scheme to optimize atom positions
> for complex systems. But, I don't know howmuch one can gain
> computationally by using PORT instead of NEWT or NEW1.
>
> Best regards
> Ravi
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