2010/4/20 Marcos Veríssimo Alves <[email protected]>: > Ian, > I guess what Andrei meant is that your cell should be, in the limit, > infinite along the z direction. I would guess that when he speaks of layers, > it is related to the length of the z axis in units of layer thickness. In > the limit of infinite z-axis length, your BZ will be 2-dimensional and all > of the states will be projected onto the same plane, hence the fact that you > can choose any kz you wish.
I understand - thanks. > One thing you could look at, and this is easy to do, is a PDOS, which you > can decompose by atoms. Selecting the PDOS only from the atoms in a given > layer, you could easily have a DOS only for those atoms at the surface. I've done that, but I wanted to invoke the BZ as well. > Marcos > > On Tue, Apr 20, 2010 at 5:22 PM, Ian Shuttleworth > <[email protected]> wrote: >> >> Thanks for the reply. Taking the limit of what you've said, Andrei - >> if you want a really slow dispersion in the k_z direction, it would >> presumably be best to work with a thin (i.e zero thickness) slab. This >> would mean the dispersion in the k_z direction should be infinitely >> slow - right? >> >> This is in fact the sort of thing I've been doing, using just the >> surface layer to 'eyeball' the 'surface' bands, then comparing this >> with the dispersions taken from the slab calculation. The problem is >> the bands tend to distort and shift in energy as the bulk is >> re-attached, making the process certainly tricky, and possibly >> unreliable. It also doesnt pick up surface states induced by the >> reattachment of the bulk. >> >> Is there any sense to taking a series of (k_x,k_y) dispersions at >> different k_z and working with them? Again, in the limit of what >> you've suggested, the sub-surface states should just fill common >> regions but I dont know if the surface states could be particularly >> enhanced in this way. >> >> On Tue, Apr 20, 2010 at 5:50 PM, <[email protected]> wrote: >> >> I'm sure this is well known to those who know, but how can I extract >> >> the surface band structure from a slab calculation? >> >> >> >> More specifically, I dealing with 10-12 layer slabs, seperated by >> >> vacuum. >> >> >> >> What do I put into the block "BandLines" to get the surface BZ, i.e >> >> the projection of the bulk BZ in the direction perpendicular to the >> >> surface? If I have the surface in the (x,y) direction, for example, >> >> how would I then set the z value of the vectors in "BandLines"? >> >> >> >> I'm guessing it's the same as the 1st BZ edge in that (z) direction, >> >> but I'm guessing... >> >> >> >> With thanks >> >> >> >> Ian Shuttleworth >> > >> > >> > Dear Ian, >> > >> > as you are interested in the dispersion over (k_x,k_y) plane only, >> > and the k_z dispersion is (hopefully) negligible, you can take >> > k_z=0 (or, any other value :-) everywhere >> > when scanning the 2-dim. Brilluin zone. In practical terms, you'll have >> > many bands which will project onto the same regions in the 2-dim BZ, >> > filling it densely (in the limit of infinitely many layers) while >> > leaving other regions open. >> > >> > Figs.6,7 of PRB65, 184412 show an example of what you may expect. >> > >> > Best regards >> > >> > Andrei Postnikov >> > >> > > >
