[Pw_forum] band and dos input files in xcrysden

[Eduardo Ariel Menendez Proupin]

Well, I also like the way the tasks are distributed, it is conceptually very
clear. I know a different code that saves a DOS file after a band
calculation and the newbies come to me with strange peaks in DOS that are
caused by a flat band along a line.
Calling dos from pw.x  or pw from dos.x masks that conceptual clarity.
However, we have to be practical and run the frequent calculations as easily
as possible. I would prepend a nscf calculation with "standard options" ,
and give warning in the otput file that non-standard options can be done
doing the nscf calculation separately.

Also, I would alway make pw.x to write the self-consistent DOS in a file
after an scf calculation, no matter how coarse is the k-points grid. I find
this useful for checking purposes (e.g. to know if an impurity have levels
in the gaps). Also, for simple metals the k-points grid needed to have
converged energies and forces also is enough to have a good DOS. Then let
the user the choice to do post processing if want a DOS with an occupation
scheme different than the SCF. I would put this file in the .save directory
and name it prefix.scfdos or something like that.

Boris, thank for your script. I will soon test it. Maybe it can be embedded
in PWGUI.

Best regards
Eduardo

---------- Mensaje reenviado ----------

> From: Paolo Giannozzi <giannozz at democritos.it>
> To: PWSCF Forum <pw_forum at pwscf.org>
> Date: Thu, 26 Feb 2009 10:34:30 +0100
> Subject: Re: [Pw_forum] band and dos input files in xcrysden
>
> On Feb 21, 2009, at 17:05 , Eduardo Ariel Menendez Proupin wrote:
>
>  Let me remind how is the process to obtain the DOS. It has three
>> calculations
>> and 3 input files
>>
>> pw.x < si.scf.in > si.scf.out   # self consistent
>> pw.x <si.dos.in > si.dos.out  # non selfconsistent dense k-points mesh
>> and a few options
>> dos.x <si.dos2.in >  si.dos2.out  # postprocessing
>>
>
> Hi Eduardo,  the issue you raise is a serious one and requires some though.
> Right now several standard calculations in q-e are clumsy because they
> require separate steps. While I think that it is a good idea to keep
> separate
> steps separate, I also think that at least the most common calculations
> might
> be streamlined. I am not convinced that the PWGui is the right tool for
> this,
> though, at least not in the present form (a tool to produce input data).
> The ideal  solution would be the usage of a high-level scripting language
> like
> python to "glue" the various pieces together, but this is highly nontrivial
> (at least for me and for 99% of q-e users).
> A simpler option could be to collapse some calculations into the same
> executable:
> for instance
> - add a call to dos after a nscf calculation in pw.x,
>  add a call to bands after a bands calculation in pw.x
> or
> - prepend a nscf calculation to dos.x,
>  prepend a band calculation to bands.x
> Suggestions are welcome
>
> Paolo
> ---
> Paolo Giannozzi, Democritos and University of Udine, Italy
>
>
>
>
>
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