[Pw_forum] VC_relax

[Vincenzo Verdolino]

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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