[Pw_forum] graphene workfunction

[Ngoc Linh Nguyen]

Giovanni Cantele wrote:
>> &inputPP
>>    outdir='/workspace/junky/WFC_2/tmp',
>>    plot_num=11
>>    filplot = 'WFC_2.2.pot'
>>   prefix='WFC_2'
>> /
>> &plot
>>    iflag=3,
>>    output_format=3,
>>    nx=10,
>>    ny=10,
>>    nz =5,
>> /
>>
>> My problem is that this is taking a really long time to run; much, 
>> much longer than the corresponding singlepoint SCF calculation ran 
>> using the same number of processors.  At this point, the pp.x has 
>> been running for 43 hours.  I can't believe that this is normal. 
>>  Here are the last couple of lines from the pp.x output file:
>
>
> I'm not very sure about that, but it could be that if you specify the 
> nx, ny, nz variables, the pp.x makes an interpolation using the 
> original FFT grid. This can be very slow, as also (if I well remember) 
> specified in Doc/INPUT_PP*. Try to specify x0, e1, e2, e3 or else 
> nothing, and maybe the original FFT grid (or a subset of it) will be 
> used instead, this should make your calculation much faster.
I think that nx=10, ny=10, and nz =5 are alright, even you can increase 
them higher for a finer mesh.
The problem could relate to that the plane wave grid is too large, with 
ecutwfc = 300 as shown in scf input files. It, for sure, make not only 
your scf run very long, but also make the grid of V very large, and pp.x 
almost stops at reading data from file.
So, you should reduce the ecutwfc value.
 
 good luck
Linh

>
> Giovanni
>
> --
>
> Giovanni Cantele, PhD
> CNR-SPIN and Dipartimento di Scienze Fisiche
> Universita' di Napoli "Federico II"
> Complesso Universitario M. S. Angelo - Ed. 6
> Via Cintia, I-80126, Napoli, Italy
> Phone: +39 081 676910 - Fax:   +39 081 676346
> Skype contact: giocan74
>
> ResearcherID: http://www.researcherid.com/rid/A-1951-2009
> Web page: http://people.na.infn.it/~cantele 
> <http://people.na.infn.it/%7Ecantele>
>                      http://www.nanomat.unina.it
>
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 Nguyen Ngoc Linh, PhD Student
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