[Wien] [Wien2k Users] Structure Generation of Solid Solution inWien2k

[Gerhard Fecher]

First a question, how is the bandstructure defined in a random alloy when the infinite periodicity is lost ?

To specify 60 % of the sites to be occupied by A, you need a supercell say with 100 atoms and 
to set 60 of the sites by A and 40 by B atoms (always one atom no fraction !) 
this you have to do for all distinguishable (!) permutations (use some statistics !)
of the site occupations, as for example
1st:      AAAAA-(60x)-AAAA BBBBB-(40x)-BBBBB
2nd:     BAAAA-(59x)-AAAA ABBBB-(39x)-BBBBB
3rd:      BBAAA-(58x)-AAAA AABBB-(38x)-BBBBB
.....
(n-1)th:   BBBBB-(39x)-BBBBA AAAAA-(59x)-AAAB 
nth:         BBBBB-(40x)-BBBBB AAAAA-(60x)-AAAA
and perform the n calculations for the different structures.

Finally you may calculate the weighted sums to find some average properties.


Actually I don't think I would perform supercell calculations to find the properties of random alloys,
just before someone complains.

Ciao
Gerhard

====================================
Dr. Gerhard H. Fecher
Institut of Inorganic and Analytical Chemistry
Johannes Gutenberg - University
55099 Mainz
________________________________________
Von: wien-bounces at zeus.theochem.tuwien.ac.at [wien-bounces at zeus.theochem.tuwien.ac.at] im Auftrag von Ghosh SUDDHASATTWA [ssghosh at igcar.gov.in]
Gesendet: Dienstag, 29. Dezember 2009 14:31
An: 'A Mailing list for WIEN2k users'
Betreff: Re: [Wien] [Wien2k Users] Structure Generation of Solid Solution       inWien2k

Dear Dr. Lawrence,
Thanks for the reply,
I have AB solid solution with A and B both occupying 10 different
nonequivalent positions.
That is to say we have a total of 10 different positions for A as well as
for B.
The atomic positions are all same.
With this, when I try to save the structure, it gives the error as same atom
cannot occupy the same atomic position.
So the struct file is not generated at all.
So how do we run supercell in this condition.

Can a solution to this be given please.
Moreover, how do we specify 60 % of the sites to be occupied by A in the
supercell program.

Thanks
Suddhasattwa Ghosh



-----Original Message-----
From: wien-bounces at zeus.theochem.tuwien.ac.at
[mailto:wien-bounces at zeus.theochem.tuwien.ac.at] On Behalf Of Laurence Marks
Sent: Tuesday, December 22, 2009 2:25 PM
To: A Mailing list for WIEN2k users
Subject: Re: [Wien] [Wien2k Users] Structure Generation of Solid Solution
inWien2k

To make a solid solution like this you need to generate a supercell
and occupy 60% of the sites with "A", and 40% of the sites with "B".
The supercell needs to be "large enough" for this to represent an
effective random distribution, and you can probably find some
literature on how large this needs to be (or maybe someone can give
relevant references).

On Mon, Dec 21, 2009 at 11:00 PM, Ghosh SUDDHASATTWA
<ssghosh at igcar.gov.in> wrote:
> Dear Wien2k users
> [SuddhasattwaGhosh]
>
> In case the crystal structure of solid solution A0.6B0.4 is available,
where
> A and B both occupy equivalent positions, is it possible to generate the
> structure using StructGen in Wien2k.
> How can mixed character of lattice points be handled in Wien2k?
>
> Suddhasattwa Ghosh
>
>
>
> _______________________________________________
> Wien mailing list
> Wien at zeus.theochem.tuwien.ac.at
> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>



--
Laurence Marks
Department of Materials Science and Engineering
MSE Rm 2036 Cook Hall
2220 N Campus Drive
Northwestern University
Evanston, IL 60208, USA
Tel: (847) 491-3996 Fax: (847) 491-7820
email: L-marks at northwestern dot edu
Web: www.numis.northwestern.edu
Chair, Commission on Electron Crystallography of IUCR
www.numis.northwestern.edu/
Electron crystallography is the branch of science that uses electron
scattering and imaging to study the structure of matter.
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