[QE-users] Charges on dopants

[Eric Glen Suter]

Dear Nicola and Matteo,


Thank you for your prompt replies and your input on this issue. I'll definitely look into some of these suggested methods.


I was wondering, however, if there are any more simplified approaches you might consider given that I only have one TM dopant in my supercell. I may very well go beyond this with future calculations, but does the fact that I only need to control the charge state of one atom in my cell simplify the matter at all?


Thank you again for your time and advice,

Eric Suter

Dept. of Physics and Astronomy

University of Georgia



Date: Wed, 26 Jun 2019 20:35:06 +0000
From: Marzari Nicola <nicola.marzari at epfl.ch>
To: Quantum ESPRESSO users Forum <users at lists.quantum-espresso.org>
Subject: Re: [QE-users] Charges on dopants
Message-ID: <707E3EF0-BD0F-41F9-81C7-7DEAA5634FE4 at epfl.ch>
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U can help, but it?s not really the answer - see some of the papers here, and search the literature:
http://theossrv1.epfl.ch/Main/OxidationStates

Sent from a tiny keyboard... Contact info:
http://theossrv1.epfl.ch/Main/Contact


Message: 4
Date: Thu, 27 Jun 2019 10:28:09 +0200
From: Matteo Cococcioni <matteo.cococcioni at unipv.it>
To: Quantum ESPRESSO users Forum <users at lists.quantum-espresso.org>
Subject: Re: [QE-users] Charges on dopants
Message-ID:
        <CAKNx695Pvg5gYog54GMvPRZNNJ60jszhizY9Fzj+D1-U1SR+AA at mail.gmail.com>
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Dear Eric,

just a couple of quick comments.
If you are already using a large supercell you can probably avoid
supercells (all this would need to be checked to be sure).
Also keep in mind that from version 6.4.1 you can find in the QE
distribution a code called HP (Hubbard parameters) that computes Hubbard U
automatically using DFPT. More details here:
10.1103/PhysRevB.98.085127.
Hope this helps.
Best regards,

Matteo


Il giorno mer 26 giu 2019 alle ore 21:51 Eric Glen Suter <esuter at uga.edu>
ha scritto:

> Hello all,
>
>
> I'm trying to simulate transition metal dopants in particular charge
> states. I'm more or less familiar with the "tot_charge" tag and how it
> functions. For these transition metals, it seems the extra charge I
> introduce doesn't want to localize on my dopants. I've been looking into
> using the Hubbard U as a way to coerce this extra electron (or hole in some
> cases) to localize on my dopant. I've read up a bit on the literature
> about these types of corrections, but I'd like to know:
>
>
> 1) Am I on the right track with this line of reasoning? I also take notice
> of the "starting_charge" tag for pw.x. I haven't tried it out, but is that
> a viable way of trying to coax the extra charge to stay on the dopant?
>
>
> 2) If Hubbard U really is the way to go, is there a way of tuning the U
> parameter that doesn't involve supercells? I'm already working with a
> pretty large cell and I don't have a ton of computational power at my
> disposal.
>
>
> I understand this is no trivial task, but if anyone has any insight on how
> to model a dopant in a particular charge state, I'd be grateful for a nudge
> in the right direction.
>
>
> Thank you in advance for any help you might have to offer,
>
> Eric Suter
>
> Dept. of Physics and Astronomy
>
> University of Georgia
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