[QE-users] Antisite and dopant calculations

[Giuseppe Mattioli]

Dear Mona Asadi Namin

Atoms in solid-state compounds cannot be generally described as the  
same atoms in solution. When you simulate Mn(II) or Ni(II) in  
solution, you actually find atomic charges fully compatible with a  
description based on the concept of "oxidation state". However, in the  
solid state the same atoms are generally involved in back-donation  
processes which alter their totaal charge, so that their atomic charge  
is not anymore compatible with their formal oxidation states. You may  
want to read this article to have an idea:

H Raebiger, S Lany, A Zunger; Nature 2008, 453, 763.

When feasible, local magnetic moment is a better indicator of  
oxidation state of atoms in solid-state systems (you may want to flick  
through the supporting information of J. Am. Chem. Soc. 2015, 137,  
10254).

HTH
Giuseppe

Quoting Mona  Asadinamin <Mona.a at uga.edu>:

> Dear all;
>
> I am doing Hubbard calculations on lithium niobate; specifically, I  
> am simulating the Nb antisite (that sits in a Li site) with charge  
> state +5.
> How do we simulate this situation in QE?
> I have set tot_charge=5 and also set the initial occupations of the  
> Nb d orbitals to zero; however after a scf iteration, the antisite  
> Nb d orbitals will gain partial occupations, similar to other Nb  
> atoms.
>
> So, how can I empty the d orbitals?
>
> This procedure is what was mentioned in the paper:
>
>
> PHYSICAL REVIEW MATERIALS 1, 054406 (2017)
>
> But, I do not understand the underlying physics. When we put a Nb  
> atom in Li site, it should lose 4 electrons and in real world these  
> are shared with oxygens in the lattice. But if we empty the Nb d  
> orbitals initially, is that physical?
>
> Best regards;
>
> Mona Asadi Namin
> Graduate student
> Center for simulational physics
> University of Georgia
> --------------------------------------
> Email:mona.a at uga.ed<mailto:mona.a at uga.edu>u<mailto:mona.a at uga.edu>
> Phone: +1-215-906-23-92



GIUSEPPE MATTIOLI
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E-mail: <giuseppe.mattioli at ism.cnr.it>