[Wien] Regarding Occupency

[Peter Blaha]

Yes, you have to use supercells.
In fact, you even have to use pretty large supercells, since you want to 
simulate low    "x"   and even for "large x" one should always use LARGE 
supercells and put in some DISORDER.

If one wants to simulate a 50:50 ALLOY, one cannot use just a 2-atom 
cell AB (since this corresponds to a "compound", but NOT an ALLOY).

An alloy is DISORDERED and you need to simulate that by some random 
distribution of the atoms in a supercell which should be as large as 
possible.

On 09/22/2013 06:49 AM, Kondaiah Samudrala wrote:
> Dear all,
>
> Presently, I am working on the DFT calculations for AB2 type layered
> materials and up to now I exactly reproduced the experimental values.
> Now, I want to change the occupancy of B atom from B2 to B(2-x), here
> x=0.0, 0.05, 0.1, 0.15,0.25... and predict the electronic properties of
> the same compound.
>
> But, I am little confuse with the calculations. i.e.  Whether I have to
> use super cells or normal unit cell for occupied AB(2-x) structures????
>
> I hope a positive reply..
>
>
>
> with regards
> Appalakondaiah Samudrala
>
>
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-- 

                                       P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
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Email: blaha at theochem.tuwien.ac.at    WWW: 
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