Yes, R cells are first converted into H (making it already 3 times
larger than the primitive R cell).
The "accepting repeat atoms at z=0" makes the non-stoichiometry. It
leads to 2 identical surfaces and inversion symmetry (cheaper calc), but
non-stoiciometry.
It is not always clear what the best model for a surface is. Yours is Te
terminated, but maybe another termination is more favorable (Bi, or
maybe another Te-layer ?)
Am 24.07.2023 um 10:51 schrieb Burhan Ahmed:
The 6ql slab is created with 1x1x2 supercell with vacuum in Z direction
and accepting repeat atoms at z=0 (using x supercell program). At first
the x supercell convert rhombohedral cell into hexagonal and then from
hexagonal cell I have created the 1x1x2 supercell and then I took the
structure suggested by sgroup.
Yes sorry for that I have used MSR1a method for the relaxation.
The force convergence is set to 1 Ry.
On Mon, 24 Jul, 2023, 2:06 pm Peter Blaha, <peter.bl...@tuwien.ac.at
<mailto:peter.bl...@tuwien.ac.at>> wrote:
I'm not sure how you get a non-stoichimetric cell with a multiplicative
number of unit cells, unless you said you want to repeat the atom at
z=0.
Of course, without this extra layer, you may not have inversion and get
2 different surface terminations in one calculation. This is the usual
problem of slabs.
Also symmetry will be reduced and "multiplicity" errors occur. But
both,
nn and sgroup create new struct files where this has been corrected.
If possible, I would also go to a smaller number of layers.
Am 24.07.2023 um 10:13 schrieb Burhan Ahmed:
> That is very true. I made the slab using the tutorial available
in the
> wien2k user manual by executing x-supercell program. What I found is
> that the 6ql supercell consist of an extra Te atom. But whenever
I try
> to remove this atom I got multiplicity error. Sir, what is best
possible
> way of making slab with vacuum or surfaces??
>
> Thanks
>
> Regards
>
> Burhan Ahmed
>
> *Research Scholar, AUS *
>
> *From: *Laurence Marks <mailto:laurence.ma...@gmail.com
<mailto:laurence.ma...@gmail.com>>
> *Sent: *Saturday, July 22, 2023 6:30 PM
> *To: *A Mailing list for WIEN2k users
> <mailto:wien@zeus.theochem.tuwien.ac.at
<mailto:wien@zeus.theochem.tuwien.ac.at>>
> *Subject: *Re: [Wien] calculation with lmbj potential
>
> Others will probably give you suggestions about converging mBJ. Some
> deeper comments.
>
> The most common reason that calculations behave badly is user error.
> Sometimes this is doing the initialization wrong, often it is
creating
> an inappropriate model. Just because one can use x supercell or
related
> codes to create atomic positions does /not/ make them sensible.
>
> Your slab has a composition Bi12 Te19, i.e. it is Te rich. You
therefore
> have a reduced, n-type semiconductor with a small gap (about 0.1eV)
> which will behave badly. If you look at your BVS you will see
that atom
> Te7 is severely underco-ordinated (unstable).
>
> I doubt that your slab will ever converge to anything which
should be
> published. Surfaces are not simple, it is unfortunately too easy
to set
> something up and get it wrong. (There are many papers in the
literature
> of dubious merit.)
>
> On Fri, Jul 21, 2023 at 10:47 PM Burhan Ahmed
<burhan.ah...@aus.ac.in <mailto:burhan.ah...@aus.ac.in>
> <mailto:burhan.ah...@aus.ac.in <mailto:burhan.ah...@aus.ac.in>>>
wrote:
>
> Dear experts, I am doing an scf calculation taking lmbj
potential.
> My system is a slab of 6ql with a vacuum of 40 ang along c-axix.
> Whenever I try to run the scf calculation including SOC,
after 999
> iteration the scf is still not converged. I have analyzed the scf
> file, it shows the fluctuating nature. At first the selected
Rmt was
> 2.5 then I reduces it to 2.34 and again convergence failed
after 999
> cycle. I have included -hdlo and -lvns 8 switch in init_lapw
as it
> shows heavy atom. I am attaching the case.struct file. Hoping for
> any suggestion/solution.
>
> Regards
>
> Burhan Ahmed
>
> *Research Scholar, AUS *
>
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> --
>
> Professor Laurence Marks (Laurie)
> Department of Materials Science and Engineering
> Northwestern University
> www.numis.northwestern.edu <http://www.numis.northwestern.edu>
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