[Pw_forum] K points in scf calculation

[Giuseppe Mattioli]

In other words, either you know very well what you need, and then you write by 
hand all of the k-points in crystal coordinates, or you use an automatic tool 
to generate a balanced grid of k-points. Remember only that:
1 - in the former case, if you want to use ONLY the k-points you write down, 
then you must (if I remember well) switch on the keyword nosym=.true.
2 - in the latter case, the total number of k-points used depends upon the 
symmetry of your system, so make some tests in order to check whether
you can afford the computational cost...

On Thursday 21 May 2009 20:49:04 Axel Kohlmeyer wrote:
> On Thu, 2009-05-21 at 19:21 +0100, Dimpy Sharma wrote:
> > Hi all,
> >
> > I am doing some scf calculations in quantum espresso, actually what I
> > want to know is about k-points . I mean when we are doing calculations
> > for a crystal, can we use k point crystal instead of k point
> > automatic? As from the manual of Quantum espresso, what I found is
>
> yes. why not?
>
> >  that k point crystal reads the
> > k points in crystal coordinates, i.e in relative coordiantes of the
> > reciprocal lattice lattice vectors while k point automatic generates
> > list of k points. I could not follow this difference properly, can
> > anyone please help me .
>
> the main difference is that with "automatic" you specify
> what kind of grid you want and QE will create the grid points
> for you, whereas with all other ways you have to specify the
> k-points explicitly.
>
> cheers,
>     axel.
>
> > Thanks
> >
> > Dimpy
> >
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   Giuseppe Mattioli                            
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