[Pw_forum] VC_relax

[Vishal Gupta]

Dear Vincenzo,
Thank you for the helpful reply. I did got the Ecut and kpoint converged,
although I have no idea why Ecut got converged to such a low value as 12.
I'll try to include the occupation smearing.
Thank you.
Best Regards,
Vishal



On Thu, Mar 31, 2016 at 11:20 PM, Vincenzo Verdolino <
vincenzo.verdolino at gmail.com> wrote:

> Dear,
>
> You should try to set the cutoff parameter to higher energy. Not sure if
> you specified the pseudopotential in your original email but i would set
> the parameter initially arount 50 Ry. Moreover you should check convergency
> on this number doing single point at different cutoff values and making
> sure your energy converged. Once you get best compromize on this parameter
> make sure your sampling on K-POINT is gonverged too. If you still
> experience issues in wf convergency you may want to include
> occupation=smearing (there are several method...try smearing=mv) and play
> with degauss in order to broad the integration for metals
>
> Hope this helps
>
> Vincenzo
>
> Inviato da iPhone
>
> Il giorno 31 mar 2016, alle ore 19:36, Vishal Gupta <
> vishal.gupta at iitrpr.ac.in> ha scritto:
>
> Dear Ari Paavo,
> Thank you for your informative reply. Can you please tell me how to
> broaden the occupation numbers ?
> Sorry,  I am a little new at this.
> Thank you.
> Best Regards,
> Vishal
>
> On Thu, Mar 31, 2016 at 9:17 PM, Ari P Seitsonen <Ari.P.Seitsonen at iki.fi>
> wrote:
>
>>
>> Dear Vishal Gupta,
>>
>>   Your cut-off energy looks _very_ low, no matter which elements/pseudo
>> potentials you do employ. Probably your system becomes metallic upon the
>> relaxation, so I would include some kind of broadening of the occupation
>> numbers, in addition possibly using the mixing mode 'local-TF', if you have
>> vacuum in your system.
>>
>>     Greetings,
>>
>>        apsi
>>
>>
>> -=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-
>>   Ari Paavo Seitsonen / Ari.P.Seitsonen at iki.fi / http://www.iki.fi/~apsi/
>>     Ecole Normale Supérieure (ENS), Département de Chimie, Paris
>>     Mobile (F) : +33 789 37 24 25    (CH) : +41 79 71 90 935
>>
>>
>> On Thu, 31 Mar 2016, Vishal Gupta wrote:
>>
>> Hi all,I've been running a vc_relax calculation on a 40 atom system. The
>>> calculation works fine for some
>>>
>>> cycles. The total force had come down to 0.108. After some time. the
>>> force started increasing and now the
>>> iterations don't converge even in 400 steps. The input file is
>>>  /
>>>  &SYSTEM
>>>                        ibrav = 0,
>>>                          nat = 40,
>>>                         ntyp = 1,
>>>                      ecutwfc = 12 ,
>>>  /
>>>  &ELECTRONS
>>>                  mixing_beta = 0.3 ,
>>>              diagonalization = 'david' ,
>>>              electron_maxstep = 200 ,
>>>  /
>>>
>>> [&Ions/]
>>> /
>>> &CELL
>>> cell_dynamics= 'sd' ,
>>> cell_dofree='xy' ,
>>> /
>>>
>>> CELL_PARAMETERS angstrom
>>>     22.265358047804796    0.000000000000000    0.000000000000000
>>>      0.000000000000000   11.131216979724510    0.000000000000000
>>>      0.000000000000000    0.000000000000000   10.000000000000000
>>>
>>> P.S. Ive tried changing cell dynamics to 'damp-pr' , 'sd' and 'damp-w',
>>> but the same problem persists.
>>> Can anybody Please help me identifying the mistake ?
>>> Thank You.
>>> Best Regards,
>>> Vishal Gupta
>>>
>>> B.Tech. 3rd year Mechanical
>>>
>>> Indian Institute of Technology Ropar
>>> Rupnagar (140001), Punjab, India.
>>> Email :- vishal.gupta at iitrpr.ac.in
>>> RMML, IIT Ropar
>>>
>>>
>>>
>>> [487a748cedfb942f92401d52262f336d11784524388949.png]
>>>
>>>
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