[Wien] Slab convergence

[Laurence Marks]

40 iterations is not much for a problem like this. I have no idea why your
calculation went strange at the end of the first run, and I doubt that
anyone can guess.

First, I assume that you bulk material is an insulator. Is your slab also
an insulator -- look at the top of case.scf2up? It is easy to get the
number of atoms wrong. I suggest checking the stoichiometry.

Second, did you check the bond valence sums? Depending upon what the atoms
are you can get these from "grep Bond *outputnn" -- they are produced by x
nn.

Third, why are you using the bulk lattice parameters? Particularly for
surfaces you need to use the DFT ones, especially in the surface plane.

Fourth, why are you not relaxing? Not only is this right, big movements
will tell you that your slab is wrong. Note: you cannot relax with -so.

I would not expect a TMDC to be hard, but I don't know details. Of course
mistakes in the model make things hard.

--
Professor Laurence Marks
Department of Materials Science and Engineering, Northwestern University
www.numis.northwestern.edu
"Research is to see what everybody else has seen, and to think what nobody
else has thought" Albert Szent-Györgyi

On Mon, Feb 20, 2023, 05:09 pluto via Wien <wien at zeus.theochem.tuwien.ac.at>
wrote:

> Dear Prof. Marks, dear All,
>
> I am calculating a large slab of one of the 1T TMDC materials, 30 unique
> atoms (this makes it 20 tri-layers, i.e. 20 vdW layers).
>
> The slab of the same material of half size, 15 unique atoms (10
> tri-layers) converged well.
>
> I am using TEMP 0.002 (first I tried with TETRA, but restated with TEMP
> after some iterations). It is a spin-polarized calculation with SOC.
> Inversion is present. Experimental lattice constant, slab made with "x
> supercell", no relaxation. Slab looks good in xcrysden ("x supercell"
> sometimes puts surface atoms wrongly, but I corrected it.). I used 30
> Bohr vacuum between layers. I use 36 k-points (klist pasted below).
> Other parameters are WIEN2k default.
>
>
>
>
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