[Wien] construction supercell

[Stefaan Cottenier]

> I am just wondering that when we start a structure like Fe(1-x)Mn(x), what
> is the starting point? to start with single Fe unit cell, enlarge it to a
> supercell (for example 2x2x2) and start putting Mn according to the
> concentration and finished with all Mn.

Correct up to here, but you should be aware of these two facts:

1) if you have e.g. 16 atoms in your supercell, you can obtain only
concentrations that are multiples of 6.25% (=1/16). Your example of 30%
cannot be realized, but by replacing 5 Fe by Mn you obtain 31.25%, which is
reasonably close. The larger the supercell, the more concentrations are
accessible (but the longer the calculations take).

2) even if you obtained your desired concentration, you have to consider
many possibilities: there are several different ways in which you can
distribute 5 Mn atoms into the 2x2x2-box (grouped together, as much
distributed as possible, a cluster of 2 and a cluster of 3, etc.). The
property you want to study is (at a fixed concentration) probably an average
over all these possibilities.

Stefaan


 Is that what poeple do normally.
> Would someone explain me for example how to construct a structure like
> Fe(0,70) Mn(0,30)?
>
>
>
>
> Yrd. Doc. Dr. Ercan UCGUN
> Dumlupinar Universitesi
> Fen Edebiyat Fakultesi
> Fizik Bolumu
> Kutahya / TURKEY
>
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