[Wien] (no subject)

[Rocquefelte]

You provide very poor information concerning your calculation. As a 
consequence it appears difficult to help you.
I can simply say that if you have used a supercell 2a x 2b x c, then a' 
= 2a = 7.18 A° at the beginning.

If after the geometry optimization you have obtained a' = 7.5 A°, it 
means that a' is overestimated by about 4.4%.

We expect an overestimation of the cell parameters from GGA, and 
underestimation from LDA. I imagine that you have selected GGA for your 
geometry optimization.

Concerning the experimental value a = 3.59 A°, i.e. a' = 2a = 7.18 A°, 
is it the dimension of the alloy or the dimension related to a pure 
phase (neglecting the impact of the substituent elements)?

Regards

Xavier



On 04/18/2012 05:03 PM, ben amara imen wrote:
> Hello!
> i'm trying to use supercell in order to determine electronic structure 
> for ternary alloy.
> When i have generated 2*2*1 supercell , i have noted that the  new 
> lattices parameters (a,b,c) are very large camparatively with the 
> starting lattices parameters
> for exp: a=3.59 A° , with supercell, a will be 7.5A° !!!!
> Also i do the optimization BUT  the value still large
> It's normal and correct  what i have found , if not  what's the problem???
> can you help me please and thanks in advance
>
>
> _______________________________________________
> Wien mailing list
> Wien at zeus.theochem.tuwien.ac.at
> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://zeus.theochem.tuwien.ac.at/pipermail/wien/attachments/20120418/b408a51b/attachment.htm>