[Pw_forum] Fluorine and PBE PAW/US

[Paolo Giannozzi]

For Ultrasoft PP it is typically convenient to have different
cutoffs for Kohn-Sham orbitals and for the charge density
(i.e. "ecutrho" > 4*"ecutwfc"; 4 is the default value).
Also note that the "nonlinear core correction" can contribute
some additional weirdness if the cutoff for the charge density
is too small

P.

On Mon, 2014-09-15 at 10:41 +0100, Benjamin Smith wrote:
> Hello,
> 
> 
> I have been running tests of PBE pseudopotentials using an F2 molecule
> within a cubic box.  For pbe-n-kjpaw, pbe-n-rrkjus and both of their
> relativistic equivalents, the convergence graph is very strange.
> There is not a smooth decline in the graph, it actually dips to a
> minimum around 35Ry, and does not satisfactorily converge until around
> 70Ry.  I have not seen a graph such as this for convergence before,
> any advice would be appreciated.
> 
> 
> Here is my input:
> 
> &control
>     prefix='testf',
>     pseudo_dir='/home/chemeng/Benjamin/ppots'
>     outdir = '/home/chemeng/Benjamin/PVDF/test',
>  /
>  &system    
>     ibrav= 1, celldm(1) =10, nat=2, ntyp= 1,
>  ecutwfc = 100 ,
>  /
>  &electrons
>  /
>  /
> ATOMIC_SPECIES
> F 18.998 F.pbe-n-rrkjus_psl.0.1.UPF
> ATOMIC_POSITIONS (crystal)
> F        0.000000000  0.00000000   0.000000000
> F        0.0 0.0 0.268
> K_POINTS automatic
> 4 4 4 0 0 0
> 
> 
> 
> Thanks.
> 
> 
> Benjamin Smith
> Visiting Researcher
> Chemical and Process Eng.
> Uni. of Strathclyde
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-- 
 Paolo Giannozzi, Dept. Chemistry&Physics&Environment, 
 Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
 Phone +39-0432-558216, fax +39-0432-558222