[Pw_forum] Convergence problem for relax calculation

[Bramha Pandey]

Hi Mitul,
As Prof. Paolo has pointed out that this system shows nature of metal so do
the calculation treating it as a metal.
In &system module, You have to write down the below three terms.

occupations  =  'smearing' ,
                   smearing  =  'mp' ,  >>>>> this is may be others also
see the input file of PW.
                   degauss  =  0.05 ,  >>>>>> this value is a arbitrary
value, Start form it and see whether you calculation converges or not, if
not then by changing this degauss and smearing from lower to higher.
In my observation if you apply more degauss value, the total energy will be
reduced so this can not be the minimum total energy. Please see the PW
forum at this points, you will get alot information regarding this issue.


On Thu, Mar 6, 2014 at 12:09 PM, Mitul Mundra <mitulm at iitk.ac.in> wrote:

> I changed the value of ecutwfc = 80 and ecutrho = 880 but the calculation
> is still not converging. In my calculations, I didn't add degauss in my
> input file, so it was using the default value of 0. Can you please suggest
> how much should I keep my degauss value at? Also, should I change smearing?
>
> Thanks
> Mitul Mundra
> Final year Dual Degree Student
> Department of Chemical Engineering
> IIT Kanpur
>
>
> On Tue, Mar 4, 2014 at 11:54 PM, Bramha Pandey <pandey.bramha at gmail.com>wrote:
>
>> Dear Mitul and Chugh,
>> (1) points will not affect any more and ignored by code itself.
>>
>> (2) points is a valid point because you are using
>> ecutwfc = 40,
>>  ecutrho = 320,
>> But by seeing the Si and Li USPP pseudo, it is suggested that
>> ecutwfc is 38 and 78 for Si and Li respectively so used max one about 80
>> and check convergence at that value.
>> ecutrho=11 to 12 times of ecutwfc for ultrasoft pseudo.
>> so it may be set 80*11=880
>>
>> By setting these parameters see the calculation if it is converged, if
>> not try from degauss as suggested earlier.
>>
>>
>>
>> On Wed, Mar 5, 2014 at 1:10 PM, <manchugh at iitk.ac.in> wrote:
>>
>>> Mitul
>>>
>>> 1. &CELL namelist is used only if Calculation is 'VC-RELAX' or 'VC-MD'.
>>> 2. Are you taking converged values of ecutwfc and ecutrho (if not, first
>>> optimize these two)?
>>>
>>> Hope this helps!
>>>
>>> Manjusha
>>> Department of Chemistry
>>> IIT Kanpur
>>>
>>>
>>> > Dear QE users,
>>> >
>>> > I am a beginner in electronic structure calculations and I have been
>>> > trying
>>> > to do relax calculations for my system. The input and output files are
>>> > attached along with this mail. My calculations are not converging and I
>>> > have tried a number of changes discussed on our forum earlier. I have
>>> > changed the value of mixing_beta from 0.7 to 0.3, I have also increased
>>> > ecutrho from 160 to 240 to 320 as I am using ultrasoft
>>> pseudopotentials.
>>> > But all my efforts have been futile till now. I would be extremely
>>> > thankful
>>> > if anyone could suggest me something which can help my calculations
>>> > converge.
>>> >
>>> > Thanks
>>> > Mitul Mundra
>>> > Final year Dual Degree Student
>>> > Department of Chemical Engineering
>>> > IIT Kanpur
>>> > _______________________________________________
>>> > Pw_forum mailing list
>>> > Pw_forum at pwscf.org
>>> > http://pwscf.org/mailman/listinfo/pw_forum
>>>
>>>
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>>
>>
>>
>> --
>> Thanks and Regards
>> Bramha Prasad Pandey
>> GLA University
>> Mathura (U.P)
>> INDIA.
>>
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>
>
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-- 
Thanks and Regards
Bramha Prasad Pandey
GLA University
Mathura (U.P)
INDIA.
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