[QE-users] hp.x - appropriate way to handle single dopant

[Abdesalem Houari]

Dear Abdul Muhaymen,
You say that your results are fine, except the band gap ! How did you correct it in pure ZnS, before Co-doping ? 
The most commun way in DFT is hybrid functionals (like HSE 06), which obviously are very demanding in computational cost.  So the DFT+U (+V) could be a nice alternative. Here I think you might need on-site U not only for Co, but also for Zn (and as you said may be S). Since ZnS is a band insulator and covalent compound, the inter-site V could play an important role.
In principle U and V parameters are neither transferable nor universal, but in your case ( calculated U from 8 atoms unit cell to use in 64 atoms supercell), I guess it should be OK !

Best regards

 

=====================================
Dr. Abdesalem HOUARI-------------------------------------------------------------------------------------------
Department of physics, Theoretical Physics Laboratory
University of Bejaia-06000. Algeria.
E-mail: abdeslam.houari at univ-bejaia.dz & habdslam at yahoo.fr
https://sites.google.com/site/houariabdeslam/homepage
===================================
 

    On Tuesday, 21 May 2024 at 04:17:30 am GMT+1, Abdul Muhaymin via users <users at lists.quantum-espresso.org> wrote:  
 
 Hello all,

I am investigating single TM dopant in wide band gap semiconductors such 
as Co in ZnS. I am using a 64 atoms supercell where I replaced one of 
the Zn atom with a Co atom. I tested several convergence with respect to 
the supercell size. My results seem fine except the band gap. Now I want 
to apply the U correction to that Co-3d (and maybe to S-2p). For this, 
is it possible to use the unit cell (8 atoms) and run hp.x to get the U 
values? Or do I have to run hp.x with the large supercell (2*2*2 unit 
cell=64 atoms)?

Also, at the beginning of our studies, during the structural relaxation 
phase, we first found our lattice parameter for the host semiconductor 
from multiple scf calculations and subsequently running an eos analysis 
(ev.x). Then we ran relax calculation but not vc-relax. We keep this 
lattice parameter constant and when introducing new dopants, we only 
vary the atomic positions (calculation='relax'). In this case, when 
running hp.x, could we replace the vc-relax calculation with relax 
calculation to self-consistently get the U values?

Thanks,
Abdul Muhaymin
Graduate (MS) student, Materials Science and Nanotechnology
Bilkent University, Ankara.

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