[CPMD-list] Help for cohesive energy!

[Ari P Seitsonen]

Dear Shyma,

On Tue, 10 May 2005, [gb2312] shyma wrote:

> Does anyone who know how to calculate the isolate atom energy? For
> example, I want to calculate the Al atom cohesive energy, firstly, I
> must to calculate the isolate Al atom energy. I calculate it but it
> seems wrong. The isolate Al atom energy value I got is -49.6285 ev and
> the primitive Al bulk energy is -55.1833 ev, so the cohesive energy is
> 5.5548 ev and it's far from the experiment value 3.39 ev and other
> calculation 3.45 ev.

> input-file 1:
>
> &SYSTEM
> SYMMETRY
> 0
> CELL
> 10.0  1.0  1.0  0.0  0.0  0.0
> ANGSTROM
> MULTIPLICITY
> 4
> SCALE
> CUTOFF
> 25
> &END

> input-file 2:
>
> &SYSTEM
>  SYMMETRY
>  2
>  SCALE
>  ANGSTROM
>  CELL
>  4.05 1.0  1.0  0  0  0
>  CUTOFF
>  30.0
>  KPOINTS MONKHORST-PACK
>   8 8 8 SHIFT=0.1 0.1 0.1
> &END

Please use the same cutoff energy in both calculations (25 vs 30 Ry).
Does that improve the results?

   BTW why do you shift the k points with 0.1/0.1/0.1?

     Greetings from Paris,

        apsi

-- 
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   Ari P Seitsonen / Ari.P.Seitsonen at iki.fi / http://www.iki.fi/~apsi/
   CNRS & IMPMC, Université Pierre et Marie Curie
       4 place Jussieu, case 115 / F-75252 Paris
   Tel: +33-1-4427 7542, Fax: +33-1-4427 3785, GSM: +33-6-6736 3820