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[Steven Homolya <Steven.Homolya@spme.monash.edu.au>]

On Wed, 22 Oct 2003 01:55 am, homegchiche@yahoo.fr wrote:
> Dear  Steven Homolya
>
> Thank you for your help and your clarifications and sorry for your time.
> With your suggestions I have corrected my input file for 2x2x2 fcc Nickel
> With one vacancy : # 8- atom cell : Nickel with one vacancy
> ...
> Do you know if there is somes method to find the inequivalent cordonnates
> of atoms in super cell such as 27 and 64 fcc cell. I just know that for 27
> atom I must use 3x3x3 fcc supercell , and for 64 4x4x4 fcc supercell. Can I
> deduce the cordonnates of other atoms with translation of 2x2x2 fcc super
> cell atom's ? I have problem to find this.
>

There is no magic wand, but it's only a handful of combinations you can have 
(because unfortunately we can't go much bigger than around 100 atoms per 
cell). You just need to work through it once, and then you can use the same 
setups on any fcc lattice. Xcrysden is a good visual aid to supercell 
construction. BTW. your reduced coordinates are still not right. I believe 
you need

xred
0.0 0.0 0.0
0.0 0.5 0.0
0.5 0.0 0.0
0.5 0.5 0.0
0.0 0.0 0.5
0.0 0.5 0.5
0.5 0.0 0.5
0.5 0.5 0.5

But before you go ahead with the calculation, you should read the 
descriptions 
of input variables acell, rprim, xred, xcart and xangst, and make sure you 
understand how these are related and how they define the unit cell.

(You might also want to have a look at variable brvltt. It may help make 
supercell construction easier, because it allows one to work with the 
conventional unit cell.)

Steve

-- 
Steven Homolya
School of Physics and Materials Engineering
Monash University VIC 3800
Australia
Tel: INT +61 3 9905 3694
Fax: INT +61 3 9905 3637