[CP2K:2239] Re: handling periodic images

Teodoro Laino teodor... at gmail.com
Sat Aug 22 03:05:04 CEST 2009

Noam Bernstein wrote:
> Hi Teo - thanks for the quick response.  The bottom line is that you're right
> about CENTER_COORDINATES.  Removing that fixed the problem.  I didn't
you're welcome
> I don't really understand the behavior, though.  The problem happens when
> you move an extremal atom, and the CENTER_COORDINATES stuff
> translates your entire molecule.  But how come it's sensitive to that, but not
> to displacements of atoms that are deeper in the molecule?  Is it just
if you translate all the atoms by a small dr the forces will be 
different as well from the non-translated one.
XC is severely modulated by the grid spacing in all PW-codes (of course 
doing DFT).
This problem can be cured in few ways but this does not mean that it 
does not exist.
> that if the whole system is translated, every atom moves a little bit, and
> the errors add up?
> I also disagree about PW codes not being translationally invariant.
> Plane waves are translationally invariant by construction.  But pretty much
well depends what si the meaning for you of "some stuff". Maybe  XC (see 
Check in the literature for the "ripples" modulation of the PES in a 


> all real codes do some stuff on a real space grid, and that breaks
> translation invariance.
> In any case, problem solved.
>                           Noam
> >

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