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[Pierre Boulenc <pierre.boulenc@isen.fr>]

Dear Stephane,

How big is your supercell for gamma-Al2O3?
Starting with the cubic spinel unit cell (which has 16 * 83.33 % 
octahedral Al, 8 tetrahedral Al and 32 O atoms), you need at least 3 
unit cells to have 8 vacancies in your whole supercell. That would bring 
you up to 160 atoms in your supercell.
I think that's quite a lot, and if you plan to calculate dielectric 
properties, you will need well-enough converged results which may take a 
huge time for such a number of atoms.

Regards,

Pierre


Stephane BECU a écrit :

> Dear abinit users,
>
> I try to build a supercell for calculating dielectric properties of 
> gamma-Al2O3. I begin with an ideal spinel unit, typified by MgAl2O4. Then I 
> do some modification of this ideal unit, one of it is to remove two Al atoms 
> to create two vacancies. The thing is I do not know how to declare the 
> vacancies:
> --> do I have to count them like the other atoms in natom?
> --> what type (typat) of atoms do I have to define?
> --> how define their positions?
>
> Thanks for your help,
>
> Stéphane Bécu
>
>  

--

Pierre Boulenc

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