[Wien] :WARNING you might have inconsistent Forces/Energies

[Peter Blaha]

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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