[Pw_forum] how to generate the pseudopotential by using virtual.x

Paolo Giannozzi giannozz at nest.sns.it
Thu Sep 20 16:41:14 CEST 2007

On Sep 20, 2007, at 15:44 , wangjunjie1981_0 wrote:

>   pseudopotentials have different mesh

the logarithmic grids used in atomic codes have the form:
    r(i) = r_0 * exp ( (i-1) dx )
(grid starting at r(1)>0) or
    r(i) = r_0 * ( exp( (i-1)*dx ) - 1.0_dp )
(grid starting at r(1)=0) where dx and r_0 are grid
parameters. Typically, r_0 is written as
   r_0 = exp(xmin) / Z
where Z is the atomic number, and one chooses xmin.
If you want the same grid with different Z, you should
choose  exp(xmin_1) / Z_1 =  exp(xmin_2) / Z_2 .
Otherwise, you have to implement some form of
interpolation between the two grids: it is not that hard.

In any event, you should really think whether mixing
Lithium and Nitrogen atoms (to get Litrogen?) using
the virtual crystal approximation is a sensible operation.
One typically uses the VCA for isovalent atoms (e.g. Si
and Ge, G and Al, ...)

Paolo Giannozzi, Dept of Physics, University of Udine
via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222

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