[Wien] Plotting the Coulomb potential

[Peter Blaha]

> I have some problem when plotting Coulomb potential for a slabs which
> mimic metal surfaces, more specifically Pd(111) and Pd(211) surfaces
> (clean and with adsorbates). I run lapw2 for energies including only
> actual valence states and then lapw5 with corresponding replacement in
> lapw5.def. Everything looks OK, except vacuum region, where I see an
> intensive noise instead of a smooth behavior. This is not periodic
> oscillation, but real noise that suggests that it originates not from
> low RKM cutoff , but from something else. My questions are:
> a) Where does it come from?
> b) How could I avoid it?

I'm a little confused: Are you plotting the Coulomb potential or the
charge density ? What has lapw2 to do with the coulomb potential ??

What is the value of rho (or V) where the oszillations occur. If it is
very small (e.g. 1.10-5 or lower, I'd still expect it is due to low RKmax
or low GMAX.
Any density in the interstital comes from the Fourier series and
GMAX/RKMAX determine the convergence of them. Check the values of
the highest (non-zero) Fourier coefficients (case.clmval or vcoul). If
this is e.g. 10-5 then you will get oszillations in this range.

Regards

                                      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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