[Pw_forum] band-structure calculations in slab-vacuum geometry: how to find the "surface k-path"?

[Ary Junior]

Hi,

If you want to compare the band structures of two different supercells, I
think you can consider the high symmetry points of the respective lattice
systems, as usual. If your slab is orthorhombic, a path

gamma X U Z gamma U R Y gamma

should be enough. See also

https://en.wikipedia.org/wiki/Brillouin_zone#Orthorhombic_la
ttice_system_ORC.281.29.2C_ORCC.281.29.2C_ORCI.281.29.2C_ORCF.283.29

Now, if your intention is discuss some localized electronic states over the
surface, I think that a projected density of states would be more
appropriated. It is not clear to me what you meant by "slab geometry", but
momentum is not precisely defined for small regions in the real space of
your system.

Ary Ferreira

FAPESP postdoctoral fellow
UFSCar - Brazil

On Sat, Apr 29, 2017 at 4:43 AM, Christoph Wolf(신소재공학과) <
chwolf at postech.ac.kr> wrote:

> Dear all!
>
>
>
> I have come across an impasse  and I am hoping for some stimulating input…
>
>
>
> I work on CsPbBr3 (cubic unit cell, a=5.6 A). I construct a  vacuum
> (5L)-slab (7L)-vacuum (5L) (L=layer numbers in multiple of the lattice
> constant in z-direction) symmetric slab (exposing the 100 CsBr terminated
> surface) and calculate the SCF/NSCF after a relax run. During relaxing the
> surface layer moves slightly “into the vacuum”, by ~5% (d12) and the next
> layer moves  slightly inwards by ~2% (d23). Pp.x gives nice electron
> density surfaces and potentials (plot_num=0,11);
>
>
>
> Now I wanted to plot the band-structure to investigate the influence of
> slab geometry on the band-structure but I am (shameful!) not sure how to
> define the k-path in order to get a “surface” band-structure. Frankly
> speaking, I am not entirely sure that would be even physically meaningful,
> but I have seen similar calculations for other slab geometries  (e.g.
> https://arxiv.org/pdf/1609.09262.pdf).
>
>
>
> I attached the input file to the nscf calculation (i.e. after the relax
> run) to illustrate the geometry, any help is greatly appreciated!
>
>
>
> Yours,
>
> Chris
>
>
>
> Postech University
>
> Materials Science and Engineering
>
> Pohang, ROK
>
>
>
>
>
> _______________________________________________
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> Pw_forum at pwscf.org
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>



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