[Wien] calculation with lmbj potential

[Peter Blaha]

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.marks at gmail.com>
> *Sent: *Saturday, July 22, 2023 6:30 PM
> *To: *A Mailing list for WIEN2k users 
> <mailto:wien at 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.ahmed at aus.ac.in 
> <mailto:burhan.ahmed at 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>
> "Research is to see what everybody else has seen, and to think what 
> nobody else has thought", Albert Szent-Györgyi
> 
> 
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-- 
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-165300
Email: peter.blaha at tuwien.ac.at    WIEN2k: http://www.wien2k.at
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