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[Masayoshi Mikami <mmikami@rc.m-kagaku.co.jp>]

Dear Kim,

You are not wrong so far... I am not familiar with your system,
but, my guess would be to make supercells (e.g. (1x1x1),
(2x2x2), (3x3x3),... as far as your computer resource allows)
to mimic the crystal, even if the supercells belong to
lower crystal symmetry group.
Computing total energies of supercells might lead to
the reason of the XRD result with the fractional occupancies.
(i.e. too small energy difference, smaller than configurational
 entropy contribution ...)

I believe that "CN" should be treated as real "CN" ionkc group,
not "X"2 ("X"=alchemical pseudopotential by mixing C and N)

Good luck,
Masayoshi

On 2007/05/28, at 15:52, Kim Allen wrote:

> Dear Abiniter,
>
> The Wyckoff position of Zn(CN)2 is as following:
> ---------------------------------------------------
> Atom  #   OX   SITE      x           y           z            
> SOF      H        ITF(U)
>  Zn   1  +2    2 a   0.25        0.25        0.25            
> 1.         0       0.0510(3)
>  N    1  -3    8 e   0.05587(19) 0.44413(19) 0.05587(19)     
> 0.5        0       0.0603(6)
>  C    1  +2    8 e   0.05587(19) 0.44413(19) 0.05587(19)     
> 0.5        0       0.0603(6)
> ------------------------------------------------
> From the above Wyckoff position, we can find that the N atom and  
> the C atom have the same Wyckoff coordinate, which bring me into  
> trouble. How to set the Xred of the N atom and the C atom?When I  
> set the 4 N atoms and 4 C atoms at the 8e postion, the calculated SG 
> (space group) is not 224. What's wrong with me?
>
> Thanks!
>
> Kim Allen