Thanks, Stefano -- inspired by your information I tried various versions of PWSCF and finally found out that a uncommitted patch that I had believed to be completely independent actually slightly messed up the forces during the SCF loop.
Will not be easy to fix the problem, but at least I have identified it now... -------- Original-Nachricht -------- > Datum: Thu, 24 Jun 2010 16:05:43 +0200 > Von: Stefano de Gironcoli <degironc at sissa.it> > An: PWSCF Forum <pw_forum at pwscf.org> > Betreff: Re: [Pw_forum] Energy conservation in Verlet-MD? > with your input on my computer the "constant" is oscillating within a > range of the order of 3e-6 . > the potential energy varies on a scale that is 1000 times larger > stefano > > Norbert Nemec wrote: > > Hi there, > > > > I am trying a very simple MD calculation (optical phonon mode of > Silicon, similar to the original Car-Parinello paper). I am surprised that the > total energy is not constant but oscillates with about 10% of the amplitude of > the potential energy. > > > > This oscillation is *independent* of the MD time step. Furthermore it > did not change with the k-grid, the energy cutoff, the functional or the > pseudopotentials. > > > > Attached is one of the input files that I used. > > > > Does anyone know what might cause this behavior? > > > > Greetings, > > Norbert > > > > ------------------------------------------------------------------------ > > > > _______________________________________________ > > Pw_forum mailing list > > Pw_forum at pwscf.org > > http://www.democritos.it/mailman/listinfo/pw_forum > > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum -- GMX DSL: Internet-, Telefon- und Handy-Flat ab 19,99 EUR/mtl. Bis zu 150 EUR Startguthaben inklusive! http://portal.gmx.net/de/go/dsl
