[Wien] Interstitial N-N pair in GaP supercell

[Kakhaber Jandieri]

Dear Lyudmila,

My final goal is to study the influence of these interstitial structures
on the structural factor.
Of course, the lattice parameters will be changed and it will have the
influence on the structural factor along with influence of atom
displacements.
But, as far as I know,  the determination of lattice parameters is more
time-consuming task.
So on preliminary stage I decided to try the supercell with unchanged
lattice constants but with relaxed atom positions.
It was just interesting for me to see what happens.
Depending on the results, I will try to determine the lattice constants
and then relax the supercell.
Anyway, I found in the literature that the distance between the
interstitial N-N atoms is around 1.4 A.
These results were for GaNAs, not for GaNP, but I guess that the
distances will not be much different in those materials.
So, in any case I am forced to reduce the RMTs and accordingly change
the cut-off energy.
Just now I am trying to relax the supercell taking RMT(Ga,P)=1.5, 
RMT(N)=1.1  and  10Ry.
As you mentioned, this value is rather usual and it was very useful
information for me.
Thank you very much for advices.

Best wishes,
Kakha




Lyudmila V. Dobysheva wrote:
>> Here is the "correct" structure file:
>>     
>
> Dear Kakha,
>
> I'd first make optimization of the cell parameters: the inserted 2 N atoms 
> instead of P should certainly expand the lattice in one direction, and maybe 
> reduce, maybe also expand in the two other directions. So, you'll receive 
> different c and a=b  (according to your struct file given).
> I am sure that after this you'll have a liitle more space for N atoms and 
> further optimization of the atoms position may be possible. If it 
> is not enough, than you should really decrease the Rmt's and, in order to 
> avoid the leakage from core, insert some core levels into the valence 
> basis. 10 Ry which you have mentioned is rather usual  as a limit for the 
> separation in such calculations.
>
> Best wishes
> Lyudmila Dobysheva
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