[Pw_forum] The relax problem

[Filipe Camargo Dalmatti Alves Lima]

By looking at the total forces. There is a part in the output that will
show the forces on the atoms and the total force of the system.

You can grep the output using this command: cat $youroutput | grep "total
force" (or something like that, I don't remember the captcha exactly). This
number should decrease along the time. If the total force reach the
threshold condition, the calculation will stop. Otherwise it can also stop
after lots of tries and it will complain saying that the convergence didn't
achieved the mininum.

For further info, the criteria for the force can be seen below:

*etot_conv_thr* REAL
Default: 1.0D-4
convergence threshold on total energy (a.u) for ionic
minimization: the convergence criterion is satisfied
when the total energy changes less than etot_conv_thr
between two consecutive scf steps. Note that etot_conv_thr
is extensive, like the total energy.
See also forc_conv_thr - both criteria must be satisfied


*forc_conv_thr* REAL
Default: 1.0D-3
convergence threshold on forces (a.u) for ionic minimization:
the convergence criterion is satisfied when all components of
all forces are smaller than forc_conv_thr.
See also etot_conv_thr (note that the latter is extensive,
forc_conv_thr is not) - both criteria must be satisfied

source:
http://www.quantum-espresso.org/wp-content/uploads/Doc/INPUT_PW.html#id3119460


Regards,

Filipe


On Tue, Apr 22, 2014 at 10:04 PM, yjunwei2012 <yjunwei2012 at 163.com> wrote:

>  Dear manchugh，
>     Thank you for your reply! I still have some problems and need your
> help. When we relax the system, how can we judge the relax result is
> successful or fail? and is there have some big different aspects between
> relax and vc-relax? Thank you again!
>
> Best wishes!
> JWY
>
>
>
> 2014-04-23
>  ------------------------------
>  yjunwei2012
>  ------------------------------
>  *发件人：*manchugh at iitk.ac.in
> *发送时间：*2014-04-23 05:04
> *主题：*Re: [Pw_forum] The relax problem
> *收件人：*"PWSCF Forum"<pw_forum at pwscf.org>
> *抄送：*
>
>  Dear JWY
>
> Your output file still has the same number of atoms. There is no problem
> with your system. You can see the missing atoms in the image you sent by
> using "Number of units drawn" option in Modify tab of xcrysden.
>
> Thank you
> Manjusha
> Ph.D student
> IIT Kanpur
> India
>
> > Hello dear QE users,
>
> >    I have used the 'calculation=relax' to calculation a 48 atomes' system,
> > and I compare the structure data(after relax) with the one from input
> > file(before relax),I find that there has a big difference. Then I
> > import the two structures to Xcrysden, the result as the above two
> > pictures show that, I do not understand why and wonder if some problems
> > with symmetry? I am not sure.
> > I look forward to your suggestion! Thank you!
> >
> > Best wishes!
> > JWY
> >
> > 2014-04-22
> >
> >
> >
> > yjunwei2012_______________________________________________
> > Pw_forum mailing list
> > Pw_forum at pwscf.org
> > http://pwscf.org/mailman/listinfo/pw_forum
>
>
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://pwscf.org/mailman/listinfo/pw_forum
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://pwscf.org/mailman/listinfo/pw_forum
>



-- 
_________________________________________
Filipe Camargo Dalmatti Alves Lima
PhD Student
University of São Paulo, Physics Institute, Materials Physics Department,
Nanomol Group, Brazil.
Phones:    (11) 3091-6881  (USP)
                (11) 97408-2755 (Vivo)
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20140422/f069fe8c/attachment.html>