[Wien] Calculation of surface state using lmbj potential with SO coupling.

[Laurence Marks]

A very basic question for you -- what is your surface structure? In
general, just taking the bulk and cutting it is wrong (too lazy).

Before what you said:
a) Optimize the volume of the bulk cell with your functional of choice, no
so or mbj.
b) Create a representative (e.g. valence neutral) surface slab using the 2D
lattice parameters in the surface plane from a).
c) Optimise the internal positions (-min) as there will be some relaxation.
Again no so or mbj. Check that you have, for instance, an insulator. You
may have to recreate the surface if you did it wrong. Depending on case you
will use run_lapw, runsp_c_lapw or runsp_lapw. Adding DW is optional.

Then start with adding mbj & so on. You have to keep your fingers crossed
that the structure from c) is a valid representation, since you cannot
optimize positions with so & mbj.

Depending upon care, 50% probability that you surface structure will be
different from nature.

--
Professor Laurence Marks (Laurie)
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 Tue, Jun 20, 2023, 07:02 Burhan Ahmed <burhan.ahmed at aus.ac.in> wrote:

> Dear experts, I am having a compact cluster with 100gb RAM, 36 cores and
> 12 TB SATA hard disk with CentOS.
>
> I want to calculate the band structure at the surface of topological
> insulator. Below are the steps I have used for the detailed calculation.
>
> After initialization, I run a pbe scf using
>
> “run_lapw -p -ec 0.0001 -cc 0.001 -NI”
>
> Save the result using
>
> “save_lapw *pbe*”
>
> In the next step
>
> “init_so_lapw” ( took the default parameters, magnetization is 0 0 1)
>
> “Init_nl_vdw “ (kernel type 1)
>
> “init_mbj_lapw”
>
> “run_lapw -p -so -i 1 -NI”
>
> “save_lapw *mbj*”
>
> “init_mbj_lapw”
>
> Took the selection 2 for surface calculation, and lmbj for potential
>
> And finally I run “run_lapw -p -lmbj -so -ec 0.0001 -cc 0.001 -i 999 -NI”
>
> And then I save the result using save_lapw *lmbj*.
>
>
>
> I want to know whether these are the correct steps for calculating band
> structure at the surface or I have to used DFT-D3 for the correction of
> dispersion which are basically used for the surface calculation. If DFT-D3
> must be used for the surface calculation to show Dirac Cone/band inversion
> nature, then what modification I have to do in my steps to use DFT-D3 so
> that I can get a clear Band structure with Dirac Cone.
>
>
>
> Thanks in Advance
>
>
>
> Regards
>
> Burhan Ahmed
>
> *Research Scholar, AUS *
>
>
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