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

[Максим Попов]

Dear Prof. Marks,

I've sent the whole output file to your private e-mail as you suggested.
Here I just put the result of grep command:

CVS version:
!    total energy              =    -242.65271405 Ry
     number of bfgs steps    =   0
!    total energy              =    -242.66331605 Ry
     number of bfgs steps    =   1
!    total energy              =    -242.66341971 Ry
     number of bfgs steps    =   2
!    total energy              =    -242.66342267 Ry
     bfgs converged in   4 scf cycles and   3 bfgs steps
!    total energy              =    -242.66284562 Ry

v.4.2.1
!    total energy              =    -242.65271405 Ry
     number of bfgs steps    =   0
!    total energy              =    -242.64460983 Ry
     number of bfgs steps    =   1
!    total energy              =    -242.66331847 Ry
     number of bfgs steps    =   1
!    total energy              =    -242.66341565 Ry
     number of bfgs steps    =   2
!    total energy              =    -242.66342170 Ry
     number of bfgs steps    =   3
!    total energy              =    -242.66342336 Ry
     bfgs converged in   6 scf cycles and   4 bfgs steps

Best regards,
Maxim.


2011/4/18 Laurence Marks <L-marks at northwestern.edu>

> The latest BFGS has a curvature trap which can change the behavior
> particularly if you have too few k-points. Can you please do
>
> grep -e "!    tot" -e bfgs WHATEVER.out
>
> (where WHATEVER is relevant) and send it to me, perhaps at my private
> email (or the full .out file). I am not an expert with QE, but might
> be able to say something.
>
> 2011/4/18 Максим Попов <max.n.popov at gmail.com>:
> > Dear QE developers,
> >
> > comparing vc-relax calculations between BFGS(4.2.1) and the latest
> BFGS(from
> > CVS) I faced  with a following problem:
> > the newest QE calculates one extra point after achieving convergence
> > criteria (etot_conv_thr,force_conv_thr,press_conv_thr),
> > which leads to slightly higher total energy.
> >
> > Here are the two latest energies from outputs:
> >        v.4.2.1                       CVS(18.04.2011)
> >
> > -242.66342170 Ry       -242.66342267 Ry
> > -242.66342336 Ry       -242.66284562 Ry
> >
> > One can see that there is a good agreement between the last energy by
> > v.4.2.1 and next to the last by CVS-version, whereas
> > the last energy by CVS is higher by ~ 0.5 mRy.
> >
> > I tried relax (cell shape fixed) also - it works fine, no extra point
> > calculation.
> >
> > --
> > Best regards, Max Popov
> > Ph.D. student
> > Materials center Leoben (MCL), Leoben, Austria.
> >
> > _______________________________________________
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> > Pw_forum at pwscf.org
> > http://www.democritos.it/mailman/listinfo/pw_forum
> >
> >
>
>
>
> --
> Laurence Marks
> Department of Materials Science and Engineering
> MSE Rm 2036 Cook Hall
> 2220 N Campus Drive
> Northwestern University
> Evanston, IL 60208, USA
> Tel: (847) 491-3996 Fax: (847) 491-7820
> email: L-marks at northwestern dot edu
> Web: www.numis.northwestern.edu
> Chair, Commission on Electron Crystallography of IUCR
> www.numis.northwestern.edu/
> Research is to see what everybody else has seen, and to think what
> nobody else has thought
> Albert Szent-Gyorgi
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