Re: [Wien] Charged cell versus virtual atom?

2022-05-02 Thread Rubel, Oleg 
I agree that Z=40.0625 was not a good suggestion. Then Z=22.0675 is reasonable 
to simulate n-doped STO. Would it be possible to verify that the additional 
charge accumulates at the surface? If I recall correctly, STO is cubic. It 
could be that the symmetry will be broken to respond to the surface dipole?

Also, I have heard about core-hole calculations. Is it completely irrelevant 
here?

Best regards
Oleg


From: Wien  on behalf of Laurence 
Marks 
Sent: Monday, May 2, 2022 10:35
To: A Mailing list for WIEN2k users
Subject: Re: [Wien] Charged cell versus virtual atom?

To clarify first: Nb-doped STO is commercial, with Nb on the Ti site doping the 
STO n-type -- Nb is 5+ valence versus 4+ for Ti. It is known that the carriers 
are delocalized.

I am interested in the near-surface band bending, both clean and with a Shottky 
contact to Pt/Pd under force. This models some of the terms in the 
trbolectricity of a moving Shottky diode contact. (This is bare-bones details.)

Band bending, but also energy (to get contact forces and bulk lattice) matter.

While having Z=22.0675 is more like V doped, it does balance the charge. 
Charged cells have approximations for the total energy, and add a background 
potential, which raises issues in my mind for the vacuum & Pd/Pt.

Simple approximations have ~80 total atoms, 25 unique; a more complete has 
~700/190 for total/unique.

To zero'th order the two look similar, but.

--
Professor Laurence Marks
Department of Materials Science and Engineering, Northwestern University
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 Mon, May 2, 2022, 5:41 AM Fecher, Gerhard 
mailto:fec...@uni-mainz.de>> wrote:
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-boun...@zeus.theochem.tuwien.ac.at]
 im Auftrag von Rubel, Oleg [rub...@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 
mailto:wien-boun...@zeus.theochem.tuwien.ac.at>>
 on behalf of Laurence Marks 
mailto:laurence.ma...@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
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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[Wien] NaNs in DOS from TETRA

2022-05-02 Thread Falke, Johannes 
Dear all,

I would just like to point out that I just ran into the problem of getting NaNs 
from TETRA despite no NaN/ being present in the qtl file in Wien2k 19.1.

I tried out this solution from 2011 which disables value-unsafe floating point 
optimizations for the Intel C++ compiler (icc). This resolved it.

https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg05281.html


I checked and Wien2K 21.1 is missing the same Makefile modification so I assume 
it can also occur there. Maybe you would like to consider adding it by default 
(maybe everywhere - "-fp-model=precise" seems to be roughly equivalent to the 
default GCC behaviour)

Best wishes,
Johannes
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Re: [Wien] Charged cell versus virtual atom?

2022-05-02 Thread Laurence Marks 
To clarify first: Nb-doped STO is commercial, with Nb on the Ti site doping
the STO n-type -- Nb is 5+ valence versus 4+ for Ti. It is known that the
carriers are delocalized.

I am interested in the near-surface band bending, both clean and with a
Shottky contact to Pt/Pd under force. This models some of the terms in the
trbolectricity of a moving Shottky diode contact. (This is bare-bones
details.)

Band bending, but also energy (to get contact forces and bulk lattice)
matter.

While having Z=22.0675 is more like V doped, it does balance the charge.
Charged cells have approximations for the total energy, and add a
background potential, which raises issues in my mind for the vacuum & Pd/Pt.

Simple approximations have ~80 total atoms, 25 unique; a more complete has
~700/190 for total/unique.

To zero'th order the two look similar, but.

--
Professor Laurence Marks
Department of Materials Science and Engineering, Northwestern University
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 Mon, May 2, 2022, 5:41 AM Fecher, Gerhard  wrote:

> 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-boun...@zeus.theochem.tuwien.ac.at] im Auftrag von Rubel,
> Oleg [rub...@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  on behalf of
> Laurence Marks 
> 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
> 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
> ___
> Wien mailing list
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Re: [Wien] Charged cell versus virtual atom?

2022-05-02 Thread 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-boun...@zeus.theochem.tuwien.ac.at] im Auftrag von Rubel, Oleg 
[rub...@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  on behalf of Laurence 
Marks 
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
"Research is to see what everybody else has seen, and to think what nobody else 
has thought", Albert Szent-Györgyi
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Re: [Wien] Charged cell versus virtual atom?

2022-05-02 Thread Peter Blaha 

I guess it depends on the kind of question you want to answer.

None of those methods will give you a reliable answer where these extra 
electrons go. Surface? Subsurface ? bulk ? localized around Nb or 
delocalized ? Relaxations around Nb ?




Am 01.05.2022 um 22:59 schrieb Laurence Marks:
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 
"Research is to see what everybody else has seen, and to think what 
nobody else has thought", Albert Szent-Györgyi


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--
--
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Phone: +43-1-58801-165300 FAX: +43-1-58801-165982
Email: bl...@theochem.tuwien.ac.atWIEN2k: http://www.wien2k.at
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