[Wien] vacuum space in slab calculation

[Peter Blaha]

> I am trying to do Si(001) slab calculation using a slab with 11 layers
> and a vacuum of  10, 15 and 20 angstrom and the potential at the center
> of the vacumm is still to large.
>
> 10 A   ->  :VZERO:v0,v0c,v0x  -1.25711  -0.60101  -0.65610 v5,v5c,v5x
> 0.33972   0.35066  -0.01093
> 15 A   ->  :VZERO:v0,v0c,v0x  -1.10002  -0.44415  -0.65587 v5,v5c,v5x
> 0.48087   0.50787  -0.02700
> 20 A   ->  :VZERO:v0,v0c,v0x  -1.19412  -0.53647  -0.65766 v5,v5c,v5x
> 0.40499   0.41492  -0.00993
>
> Should I still increase the vacuum in the cell? is it normal such a
> large value?

I see nothing wrong with those numbers except that I would have expected
some monotonous decrease with vacuum size. Maybe you mixed two lines ?
It seems your vacuum is at z=0.5 ?

Compare the difference between v5c and the respective Fermi energies. This
gives the work function and this should "converge" with respect
to vacuum size.

                                      P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-15671             FAX: +43-1-58801-15698
Email: blaha at theochem.tuwien.ac.at    WWW: http://info.tuwien.ac.at/theochem/
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