[Pw_forum] convergence test for chromium

[Duy Le]

Hi,
The USPP which includes sp semicore could lead you to that such ecut if it
is not a very good PP. Ecutrho should be about 10-14*ecut and you should
also make sure that the k-point sampling is good enough.
Good luck.

On Wed, Sep 30, 2009 at 2:15 PM, Ary Junior <aryjunior at gmail.com> wrote:

> Hi Lorenzo, I did exactly what you said and I got the same convergence
> chart on both tests... I'm working with g-alumina and ultrasoft pp... My
> first convergence test suggested an ecutwfc value between 50Ry-70Ry... Then
> I used ecutrho = 280Ry for the second test... It means that I can use
> ecutrho = 4*ecutwfc, right?
>
> []s
>
> Ary Junior
>
>
> On Wed, Sep 30, 2009 at 1:00 PM, Lorenzo Paulatto <paulatto at sissa.it>wrote:
>
>> In data 30 settembre 2009 alle ore 17:48:41, udayagiri sai babu
>> <udayagiri3 at gmail.com> ha scritto:
>>
>> > Dear all
>> > I did convergence tests for chromium. The ecut value i obtained for
>> > energy converged to 1mRyd is 60Ryd! which i believe is very high for an
>> > Ultra Soft PP can somebody tell me if i am doing something wrong. Given
>> > below are my
>> > sample input file and ecut vs total energy.
>>
>> Dear Udayagiri,
>> what about the cutoff for charge density?
>> One good procedure to find a nicely converged cutoff is to increase
>> ecutwfc until it converges than set ecutrho to 4*ecutwfc and reduce
>> ecutwfc keeping ecutrho fixed.
>>
>> Maybe you can fix ecutrho to 240 and see how low you can go with ecutwfc
>>
>> best regards
>>
>>
>> --
>> Lorenzo Paulatto
>> SISSA  &  DEMOCRITOS (Trieste)
>> phone: +39 040 3787 511
>> skype: paulatz
>> www:   http://people.sissa.it/~paulatto/<http://people.sissa.it/%7Epaulatto/>
>>
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>
>
>
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-- 
--------------------------------------------------
Duy Le
PhD Student
Department of Physics
University of Central Florida.
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