[CPMD-list] PCG MINIMIZE with ROKS (MODIFIED GOEDECKER)

[Eneritz Muguruza gonzalez]

Dear Irmgard,

> ROKS with MODIFIED GOEDECKER may show upwards convergence. That is
> perfectly fine. The modification of the Goedecker algorithm was 
> necessary for excited states that have the same symmetry as the ground 
> state (e.g. pi-pi*).

       Thank you very much for your answer. In my PCG MINIMIZE
calculations I observe the upward convergence, initially it might look
like there is a lower energy minimum, but then the energy goes up no
matter which recipe I use and converges to the same value obtained with
ODIIS. But I don't understand this upward behaviour.

Does this mean that the algorithm is not variational at each step? that
it might give unphysical energies at intermediate steps? 
Is it possible that the modified Goedecker algorithm coupled to the line
search of PCG MINIMIZE does not fully prevent the orbital rotation when
is far from convergence, thus giving unphysical intermediate solutions
(in fact lower in energy than the correct one)? 

The converged ROKS energy without the modified Goedecker is
in fact lower (E=-103.7189 Ha).

Many thanks in advance,


          Eneritz






>  Hello,
> > 
> > 
> >     This is me again, I just notice that I made a mistake in the mail I
> > sent. The final energy obtained combining the PCG MINIMIZE and ODIIS
> > methods is the same obtained with the other methods(ODIIS): E=-103.6901
> > Ha.
> > 
> >    Sorry about the confusion,
> > 
> > 
> >           Eneritz 
> > 
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