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Thanks, Guido.<br>
<br>
<pre>Are atoms moving considerably, meanwhile?</pre>
<br>
Yes, they are.<br>
<pre>
do you really need so large ecutrho and small mixing_beta?</pre>
<br>
There is no necessity about a large ecutrho. Which value do you
think is more suitable?<br>
<br>
For mixing_beta, I tried the default value, but the program always
stopped with some error, which I do not remember anymore. Then, I
followed the suggestion of FAQs to try a value between 0.1 and 0.3..
<br>
<br>
Pedro Moreira<br>
IFGW-Unicamp-Brazil<br>
<br>
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<th align="RIGHT" nowrap="nowrap" valign="BASELINE">Assunto: </th>
<td>Re: [Pw_forum] A long relaxation</td>
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<th align="RIGHT" nowrap="nowrap" valign="BASELINE">Data: </th>
<td>Fri, 18 May 2012 09:44:24 +0200</td>
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<td>Guido Fratesi <a class="moz-txt-link-rfc2396E"
href="mailto:fratesi@mater.unimib.it"><fratesi@mater.unimib.it></a></td>
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<td><a class="moz-txt-link-abbreviated"
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<pre>Dear Pedro,
if the energy is decreasing you are not trapped in a local minimum (not
yet, at least: maybe you are approaching it).
From the extract you sent us, forces are rather increasing than
oscillating, and if the energy is instead decreasing that suggests me
that your system started close to some saddle point or energy maximum,
then after some relaxation steps it found some stronger energy gradient
and started following it.
Are atoms moving considerably, meanwhile?
PS do you really need so large ecutrho and small mixing_beta?
Best,
Guido
On 05/17/2012 08:07 PM, Pedro Augusto F. P. Moreira wrote:
> Dear all,
>
> I am doing a relaxation which is consuming a very long time. My input
> is below, but I think it is OK, because there is nothing wrong with my
> output and the system energies are decreasing .
> However, I have noted that the total forces and the forces acting on
> each atoms have oscillated a lot. I summarized below the total forces,
> which are showed in the end of each SC calculation.
> Is it right? Or could the program find a local minimum and cannot get
> out of it (or anything similar)?
>
> Thanks a lot,
>
> Pedro
>
> ####Total forces#####
> Total force = 0.162129 Total SCF correction = 0.000046
> Total force = 0.131410 Total SCF correction = 0.039799
> Total force = 0.199885 Total SCF correction = 0.004809
> Total force = 0.254130 Total SCF correction = 0.004143
> Total force = 0.285538 Total SCF correction = 0.003092
> Total force = 0.339246 Total SCF correction = 0.001453
> Total force = 0.419218 Total SCF correction = 0.000630
> Total force = 0.509140 Total SCF correction = 0.000243
> Total force = 0.593476 Total SCF correction = 0.000133
> Total force = 0.534968 Total SCF correction = 0.000206
> Total force = 0.431853 Total SCF correction = 0.004582
> Total force = 0.308932 Total SCF correction = 0.000404
>
> #####Input########
> &control
> calculation='relax',
> restart_mode='from_scratch',
> pseudo_dir = '/quantum-espresso/espresso/pseudo/',
> outdir='/quantum-espresso/espresso/tmp/',
> prefix='ap5',
> tprnfor = .true.,
> nstep = 1000,
> /
> &system
> ibrav = 4, celldm(1) = 17.8749, celldm(3) = 0.7241,
> nat = 42, ntyp = 4,
> ecutwfc = 52.0, ecutrho = 900.0,
> /
> &electrons
> electron_maxstep = 500
> mixing_beta = 0.1,
> /
> &ions
> ion_dynamics='bfgs',
> /
> ATOMIC_SPECIES
> Ca 40.0780 Ca.pz-n-vbc.UPF
> P 30.9738 P.pz-van_ak.UPF
> O 15.9994 O.pz-van_ak.UPF
> F 18.99840 F.pz-van_asa.UPF
> ATOMIC_POSITIONS angstrom
> .
> .
> .
> ##############################
>
--
Guido Fratesi
Dipartimento di Scienza dei Materiali
Universita` degli Studi di Milano-Bicocca
via Cozzi 53, 20125 Milano, Italy
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