[Pw_forum] new bfgs: strange behavior doing vc-relax

[Paolo Giannozzi]

On Apr 20, 2011, at 16:02 , Eduardo Ariel Menendez Proupin wrote:

> I am not sure if the calculation is still variational with  
> ultrasoft pseudopotentials

it should be

> or even if the Hohenberg-Kohn lemma is valid with non local  
> pseudopotentials

there is some old work by Gilbert on this subject: http://prb.aps.org/ 
abstract/PRB/v12/i6/p2111_1

> With QE I have always seen the energy to decrease when the cutoffs are
> increased, but with VASP, I always see an oscillation in the total  
> energy
> when the cutoff is incremented.

just guessing: it might be a consequence of real-space treatment of  
augmentation
functions.

P.
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Paolo Giannozzi, Dept of Chemistry&Physics&Environment,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222