[Pw_forum] k points in epsilon.x

[Stefano Baroni]

oops ...
many other picky Italian speaking members of this list ...

S.

On Oct 13, 2009, at 9:30 AM, Gabriele Sclauzero wrote:

> First:
>
>    Andrea Ferretti is Sir, Layla Martin Samos is Madam, not the  
> opposite...
>
> dev sharma wrote:
>> Dear Madam,
>>
>> May be my question was not clear to all. originally my question was  
>> the
>> same . That as u suggested do a scf and then  a nscf with the nbnd  
>> and
>> regular mesh of k points. What i want to know , that in nscf  
>> calculation
>> i have to give
>> kpoints {automatic}
>> 4 4 4
>> or like
>> Kpoints
>> 72
>> 0 0 0
>> 0 0.1 0
>> /
>> /
>> 0.5 0 0
>>
>> and i asked that if i have to give k points in second option, How to
>> give that ????  can i give these 72 k points generated by the scf
>> output  ????
>
> Second:
>
> Many people has already replied you, giving different possible  
> solutions to your problem.
> I'm quite astonished that after a dozen of mails we have not been  
> able to close this
> thread. Maybe there is some problem in communication/understanding  
> which I cannot capture.
> I summarize what are the possible solutions if you still want to use  
> epsilon.x and don't
> want to try Yambo or SaX and co.
> In the nscf run, either use
>
> nosym=.TRUE.
> noinv=.TRUE.
>
> K_POINTS AUTOMATIC
> 4 4 4 0 0 0
>
> Such that the code will NOT use symmetry to reduce the 4x4x4 k-point  
> mesh.
>
> Or use:
>
> nosym=.TRUE.
>
> K_POINTS CRYSTAL
>
>
> and then append a list of k-points corresponding to a 4x4x4 regular  
> grid of key points
> that you can easily generate either using the piece of code given by  
> Layla, or adapting
> the code in pwtools/kpoints.f or PW/kpoint_grid.f90.
>
> Obviously you must test for convergence with respect to the BZ  
> sampling (i.e. number of
> k-points)
>
> HTH
>
>
> GS
>
>
>
>
>
>
>
>> Thnaks
>> Dev Sharma,
>> Unoveristy of Delhi
>>
>> On Mon, Oct 12, 2009 at 8:21 PM, Andrea Ferretti <ferretti at mit.edu
>> <mailto:ferretti at mit.edu>> wrote:
>>
>>
>>
>>    Hi,
>>
>>> Sir, i want to calculate dielectric constant as a function of
>>    frequency.  I
>>> have read the manual And it is written there that
>>> Epsilon.x doesn't support the reduction of the k-points grid into  
>>> the
>>> unreducible Brillouin zone, so the previous PW runs must be
>>    performed with a
>>> uniform k-points grid and all k-points weights must be equal to
>>    each other,
>>> i.e. in the k-points card the k-points coordinates must be given
>>    manually in
>>> \emph{crystal} or \emph{alat} or \emph{bohr}, but not with the
>>> \emph{automatic} option.
>>> Thanks
>>>
>>
>>    I think this is correct..
>>    a good procedure could be first to run a scf calculation using  
>> whatever
>>    symmetrized kpt-mesh. Then you can run a nscf calculation with a
>>    suitable
>>    number of empty bands (according to your needs) and a regular mesh
>>    of kpts
>>    over the whole BZ.
>>
>>    andrea
>>
>>    DMSE, MIT
>>    Massachusetts
>>
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>>
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> -- 
>
>
> o ------------------------------------------------ o
> | Gabriele Sclauzero, PhD Student                  |
> | c/o:   SISSA & CNR-INFM Democritos,              |
> |        via Beirut 2-4, 34014 Trieste (Italy)     |
> | email: sclauzer at sissa.it                         |
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---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center -  
Trieste
http://stefano.baroni.me [+39] 040 3787 406 (tel) -528 (fax) /  
stefanobaroni (skype)

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