[Wien] Charged cell versus virtual atom?

[Fecher, Gerhard]

Z=40.0625 means you replace all Ti by Zr + a little electrons, instead of Ti + 1/16 e-, isn't it ?
I assume that changing the charge by epsilon e- works only for neighbouring elements, on top,  if you rplace the Z of Ti (22) by 22+1=23 then you have fully V and not Ti+1/2 Cr, etc..

==> supercell even if its vast     (or some program that uses CPA to have a mean field behaviour).

Ciao
Gerhard

DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy:
"I think the problem, to be quite honest with you,
is that you have never actually known what the question is."

====================================
Dr. Gerhard H. Fecher
Institut of Physics
Johannes Gutenberg - University
55099 Mainz
________________________________________
Von: Wien [wien-bounces at zeus.theochem.tuwien.ac.at] im Auftrag von Rubel, Oleg [rubelo at mcmaster.ca]
Gesendet: Montag, 2. Mai 2022 05:19
An: A Mailing list for WIEN2k users
Betreff: Re: [Wien] Charged cell versus virtual atom?

I must admit that I do not have any experience with the fractional Z, but it seems that the option (b) could be better. At least it has some chemical specificity. Maybe it is better to use Z=40.0625 to differentiate between Nb and V?

Best regards
Oleg

________________________________________
From: Wien <wien-bounces at zeus.theochem.tuwien.ac.at> on behalf of Laurence Marks <laurence.marks at gmail.com>
Sent: Sunday, May 1, 2022 16:59
To: A Mailing list for WIEN2k users
Subject: [Wien] Charged cell versus virtual atom?

As part of a larger problem, I need to simulate a Nb-doped SrTiO3 surface, where 1/16 Ti sites is Nb. To first order this is 1/16 extra electrons. There are two ways I can think of to do this:
a) Charged cell calculation, with extra electrons + background charge.
b) Virtual atom, where the Ti's have a Z of 22.0625.

Does anyone have any experience with something similar? I can think of reasons why both have issues, e.g. the extra potential in the vacuum in a).

N.B., doing a super-duper surface cell with 1/16 Ti changed is too vast.

--
Professor Laurence Marks
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
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