[Wien] Surface Wavefunction Oscillating

[Peter Blaha]

>   Has anyone seen that the wavefunction in the vacuum region
> of a surface starts from some smooth exponential decay
> and then becomes oscillatory?
>   I am working on Cu(111) surface and see the above
> behavior (for both surface and bulk states). I suspect
> the oscillation is related to some kind of insufficient
> precision but don't know what it is exactly. The calculation
> is done with 4000 k points and charge convergence 0.00001.
> Can anyone explain or/and resolve this phenomenon?

Are you talking about wavefunctions, charge densities or potentials ?

If it happens far away from the surface, we are aware of a problem coming
from GGA. GGA in the low density region has problems with large scaled
gradients and there are different cutoffs in the program, which
set a certain small density to zero, or use LDA froma certain density on,...
This may cause some small wiggles in the xc-potential which then
may produce some wiggles in wavefunctions and densities.

So far, however, all tests showed no influence on the underlying physics.

                                      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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