[Wien] How to choose the substitution site when performing the calculation of doping?

[Jian Zhu]

Well-beloved Stefaan Cottenier,
   Thank you very much for your valuable and informative advice. Taking the
2*2*2 supercell of TiC as the example, would you like to give me some advice
on how to substitute the original atoms of supercell according to the two
different instances:(1)impurities that are closely packed into clusters,
(2)impurities that are as homogeneously disitributed over the supercell as
possible?
   Besides, how about the substitution of original atoms when there are more
than one type original atom (for example the Si atom in FeSi2) in the
supercell? Thank you very much.
   Best regards.

Sincerely yours,
                                                                     Fei Tun



2006/9/26, Stefaan Cottenier <Stefaan.Cottenier at fys.kuleuven.be>:
>
> Jian Zhu wrote:
>
> > Dear all wien2k users,
> >    Recently, when I perform the doping calculation, I encounter an
> > uncertain problem. I need your confirmation. When performing doping
> > calculation, I construct a supercell firstly.Then one or several
> > congeneric atoms are substituted by one impurity atom or several
> > impurity ones. Taking TiC as the example, there are two atoms in a TiC
> > unit cell, i.e. one C atom and one Ti atom. There are 16 atoms in the
> > supercell after a 2*2*2 supercell is created, i.e. 8 C atoms and 8 Ti
> > ones. Now, I am planing to substitute one C atom with one N atom. My
> > problem is which C atom among 8 C atoms should be chosen to be
> > substituted by one N atom? Any C atom is ok?
>
> Yes. As there is only one type of C-atom in your original cell, it
> doesn't matter which one you replace in the supercell.
>
> > Furthermore,when the number of atoms more than one  in the supercell
> > are chosen to be substituted by impurity atoms, how to choose the C
> > atoms to be substituted by N atoms?
>
> That of course depends on the physics you want to study. Do you want
> impurities that are closely packed into clusters, or rather impurities
> that are as homogeneously disitributed over the cell as possible? Or
> something in between? The choice is up to you.
>
> Stefaan
>
>
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-- 
Scoool of Materials Science and Engineering
Central South University
Jian Zhu
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