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

[Stefaan Cottenier]

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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