[Pw_forum] vc-relax calculation

Julen Larrucea julenlist at gmail.com
Mon Nov 11 12:29:16 CET 2013


Dear Ehsan,
As Sanjeev pointed out, it is a good to attach your error message when
asking for help.

After running your example, I get the following error message:

.....................................................................................................
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
     Error in routine  read_namelists (1):
      reading namelist cell
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
     stopping ...
.....................................................................................................

Which raises due to the fact that you are performing a cell relax
calculation, but you have not included the &CELL section (an empty one is
OK too). You can skip it for a normal "relax" or "scf" calculation, but not
for "vc-relax".
So modify your input as:
.....................................................................................................
...
&IONS
/
&CELL
/
CELL_PARAMETERS {angstrom}
 9.83804859    0.00000000    0.00000000
 4.91902429    8.52000000    0.00000000
 0.00000000    0.00000000   12.00000000
...
.....................................................................................................

Let me add you a couple of suggestions for your input.

- Your conv_thr is way too big. 1.D-6 should be enough for a relaxation,
and if you want higher accuracy for the electronic properties, just run an
scf on the last structure with 1.D-8.

- When you run a cell relaxation, you should use about 3 times the
recommended ecutwfc and ecutrho, so yours is way too small in any case.

- The pseudo potential file in the QE website you are using does not
provide any suggestions for minimum ecutwfc and ecutrho, so I just used a
simple script to check it:


 -10.7675 ++-----+------+-------+------+------+------+-------+------+-----++
              +      +     './energies.ecutwfc.C.pw91-van_ak.UPF' u 1:2
****** +

****                                                                       |
  -10.768 ++  **
      ++
              |
*                                                                  |
-10.7685 ++      **
      ++
              |
*                                                               |
              |
**                                                            |
  -10.769 ++             *
      ++
              |
*                                                         |

|
|
-10.7695 ++
****                                                   ++
              |
***                                                 |
              |
*                                                 |
   -10.77 ++
**************                              ++
              |
*******                          |
 -10.7705 ++
********              ++
              |
*******         |
               +      +      +       +      +      +      +       +
********
  -10.771 ++-----+------+-------+------+------+------+-------+------+-----++
            30     40     50      60     70     80     90     100    110
120

(It does not look very clear, but you can run this script by yourself and
check it in better quality, it only takes a few minutes to run.
http://www.larrucea.eu/checking-optimum-cutoff-qe/)

So, you should use an ecutwfc of around 110 Ry for your normal calculations
and about 330 Ry for the cell relaxations.

  Best regards

   Julen








On Mon, Nov 11, 2013 at 2:18 AM, Sanjeev Gupta <physics.skgupta at gmail.com>wrote:

> can you post the error?
>
> bests
> sanjeev
>
>
> On Sun, Nov 10, 2013 at 11:43 AM, ehsan targholi <targholi at gmail.com>wrote:
>
>>
>> *hi*
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>> *dear all, thanks  for reply to my earlier question. i want to optimize
>> graphene , but i have problem in vc-relax calculation. my input is :
>> &control  calculation = 'vc-relax' ,  restart_mode='from_scratch'
>> prefix='gs32'  wf_collect =.true  pseudo_dir =
>> '/home/ehsan/espresso/upf_files/',   outdir
>> ='/home/ehsan/espresso/tmp/'/&system  ibrav=0  nat=32  ntyp=1  nbnd=128
>> ecutwfc=45  ecutrho=450/&electrons  mixing_beta=0.7  conv_thr = 1.0e-12
>> /&IONS/CELL_PARAMETERS {angstrom} 9.83804859    0.00000000
>> 0.00000000 4.91902429    8.52000000    0.00000000 0.00000000
>> 0.00000000   12.00000000ATOMIC_SPECIESC 12.011 C.pw91-van_ak.UPF
>> ATOMIC_POSITIONS {angstrom} C                  3.07439018    1.77499927
>> 0.00160788 C                  0.61487804    0.35499985
>> 0.00032158 C                  5.53390233    1.77499927
>> 0.00160788 C                  7.99341448    1.77499927    0.00160788
>>  C                 10.45292662    1.77499927
>> 0.00160788 C                  3.07439018    0.35499985
>> 0.00032158 C                  5.53390233    0.35499985
>> 0.00032158 C                  7.99341448    0.35499985    0.00032158
>>  C                  4.30414626    3.90499840
>> 0.00353734 C                  5.53390233    6.03499752
>> 0.00546680 C                  6.76365840    8.16499665
>> 0.00739626 C                  1.84463411    2.48499898    0.00225103
>>  C                  3.07439018    4.61499811
>> 0.00418049 C                  4.30414626    6.74499723
>> 0.00610995 C                  6.76365840    3.90499840
>> 0.00353734 C                  7.99341448    6.03499752    0.00546680
>>  C                  9.22317055    8.16499665
>> 0.00739626 C                  9.22317055    3.90499840
>> 0.00353734 C                 10.45292662    6.03499752
>> 0.00546680 C                 11.68268270    8.16499665    0.00739626
>>  C                 11.68268270    3.90499840
>> 0.00353734 C                 12.91243877    6.03499752
>> 0.00546680 C                 14.14219484    8.16499665
>> 0.00739626 C                  4.30414626    2.48499898    0.00225103
>>  C                  5.53390233    4.61499811
>> 0.00418049 C                  6.76365840    6.74499723
>> 0.00610995 C                  6.76365840    2.48499898
>> 0.00225103 C                  7.99341448    4.61499811    0.00418049
>>  C                  9.22317055    6.74499723
>> 0.00610995 C                  9.22317055    2.48499898
>> 0.00225103 C                 10.45292662    4.61499811
>> 0.00418049 C                 11.68268270    6.74499723    0.00610995
>> K_POINTS {automatic}16 16 1 0 0 0*
>>
>>
>> *but espresso give error. please help me to insert correct input for
>> variable relax calculation. *
>>
>> *ehsan targholi *
>>
>> *graduate student of chemistry department of iust *
>>
>>
>> _______________________________________________
>> Pw_forum mailing list
>> Pw_forum at pwscf.org
>> http://pwscf.org/mailman/listinfo/pw_forum
>>
>
>
>
> --
> With Best Regards,
>
> ------------------------------------
> Dr. Sanjeev Kumar Gupta
> Fulbright Post-Doctoral Scholar
> Dept. of Physics
> Michigan Technological University
> 1400 Townsend Drive, Houghton
> MI 49931, USA
> ------------------------------------
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://pwscf.org/mailman/listinfo/pw_forum
>



-- 

-- 
Dr. Julen Larrucea
Postdoctoral researcher,
BCCMS, HMI Group, University of Bremen
Phone: +49 421 218 64582
Fax: +49 421 218 64599
 http://www.larrucea.eu
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