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

Tue Jun 20 11:20:33 CEST 2023

DFT-D3 is a method for van der Waals interactions, which are not well 
described by GGA or mBJ. It has nothing to do with SO, ....

If you have optimized your system in PBE and it "works", you don't need 
DFT-D3 (which is anyway often problematic for heavier atoms or TMs).

Am 20.06.2023 um 11:02 schrieb Burhan Ahmed:
>
> Yes,
>
>  1. I have optimized the bulk cell (with PBE) without so or mbj
>  2. The slab is constructed from the optimized cell. I have generated
>     a supercell 1x1x2 with a vacuum of 40ang and from that a slab of
>     6ql (quintuple layers) is generated. The space group then changes
>     from 166-R3m to 164-p3m1 keeping the same hexagonal cell.
>  3. After that I have minimized the internal atomic position
>     (relaxation) using msr1 method as available in wine2k code.
>
> Now my question is that, I want to calculate the band structure for 
> the slab with SO coupling. The steps I have mentioned are the correct 
> one or I have to use the DFT-D3 correction. If DFT-D3 is a must one 
> for the topological band structure then what modification/new steps 
> required for the calculation.
>
> Regards
>
> Burhan Ahmed
>
> *Research Scholar, AUS *
>
> *From: *Laurence Marks <mailto:laurence.marks at gmail.com>
> *Sent: *Tuesday, June 20, 2023 9:48 AM
> *To: *A Mailing list for WIEN2k users 
> <mailto:wien at zeus.theochem.tuwien.ac.at>
> *Subject: *Re: [Wien] Calculation of surface state using lmbj 
> potential with SO coupling.
>
> 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 <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
>
> 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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-- 
-----------------------------------------------------------------------
Peter Blaha,  Inst. f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-158801165300
Email:peter.blaha at tuwien.ac.at           
WWW:http://www.imc.tuwien.ac.at       WIEN2k:http://www.wien2k.at
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