[Pw_forum] local and global minimums in relaxation

[Mike Marchywka]

btw, where are old posts archived, I wanted to post these comments on Linked In
Computational chemistry group to explain my reaction to a post someone
else made there earlier ( see link to water model below). 



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> From: marchywka at hotmail.com
> To: pw_forum at pwscf.org
> Date: Thu, 27 Dec 2012 11:44:44 -0500
> Subject: Re: [Pw_forum] local and global minimums in relaxation
>
>
>
>
>
> > Date: Mon, 24 Dec 2012 23:20:34 -0500
> > From: correlation at tut.by
> > To: pw_forum at pwscf.org
> > Subject: Re: [Pw_forum] local and global minimums in relaxation
> >
> > I see..
> > Thank you!
>
> Well as I understand the situation, normally you have a molecule that you want to
> optimize and hope your original structure is close enough that the "forces" the minimizer
> sees get it to the right answer. Most molecules are not in some global minimum configuration
> of atoms right? You could take atoms infinitely far apart I guess and see what you get.
>
> Personally though I did have a related question and that is what is neglected by trying to
> find a static ground state and ignoring any fluctuations? This is probably not yet
> relevant compared to errors in getting static result but curious if anyone wanted to comment.
>

This was just posted on the linked in Computational Chemistry group, showing importance
of fluctuation in understanding water, thought it was relevant to my earlier comment LOL

http://www.rsc.org/chemistryworld/2013/02/water-structure-tetrahedral-controversy-xas-xafs



>
>
>
> >
> > Sergey
> >
> > On 12/21/2012 3:47 PM, Paolo Giannozzi wrote:
> > > On Dec 21, 2012, at 20:01 , Sergey wrote:
> > >
> > >> when I do relaxation (using bfgs algorithm), I end up with the
> > >> system in
> > >> one of the minimums. It can be local one or it can be global one. And
> > >> there is probably several other possible local minimums in the system.
> > >> How can I publish such a result? As I see in the papers no one usually
> > >> describe this issue. Usually it is just - 'we performed structural
> > >> optimization (relaxation) and here is the result.'
> > >>
> > >> How to deal with this matter?
> > > if you find a better way to deal with this matter, your future career is
> > > guaranteed. It is a well-known problem. That's way smart people
> > > have invented simulating annealing, genetic algorithms,
> > > metadynamics, ...
> > >
> > > P.
> > > ---
> > > Paolo Giannozzi, Dept of Chemistry&Physics&Environment,
> > > Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
> > > Phone +39-0432-558216, fax +39-0432-558222
> > >
> > >
> > >
> > >
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