[ase-users] Re: [Campos-devel] About the STM class, GPAW and ASE3

[Jens Jørgen Mortensen]

On Wed, 2009-01-14 at 16:37 +0200, Pentti Frondelius wrote:
> Dear all,
> 
> I could not find a very exact documentation of the STM class in ASE3.
> Thus, I would like to ask, what the following lines in the code do
> 
> class STM:
> ...
>     def calculate_ldos(self, width=None, bias=0.0):
> ...
>         if 0 in self.symmetries:
>             ldos[1:] += ldos[:0:-1].copy()
>             ldos[1:] *= 0.5

(x,y) -> (-x,y)

>         if 1 in self.symmetries:
>             ldos[:, 1:] += ldos[:, :0:-1].copy()
>             ldos[:, 1:] *= 0.5

(x,y) -> (x,-y)

>         if 2 in self.symmetries:
>             ldos += ldos.transpose((1, 0, 2)).copy()
>             ldos *= 0.5

(x,y) -> (y,x)

> I suppose that they have something to do with the symmetries of the
> original k-point set and their reduction to the irreducible Brillouin
> zone.

Yes.

> It would be nice if someone could explain those lines. It seems that
> the symmetry parameters should be given for the tool by hand.

Yes.

>  How
> those should be used?

Use "stm = STM(atoms, symmetries=[0, 1, 2])" if you have all symmetries
mentioned above.

>  In what cases they are needed?

If you used symmetries to reduce the number of k-points, then you must
specify those symmetries when you create the STM tool.

Jens Jørgen

PS:  I'm also sending this to the ase-users list - which is the correct
mailing list for this kind of stuff.

> Regards,
> Pentti Frondelius
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