[Wien] Obtaining the Reference Energy for Calculated Band Structure

[Peter Blaha]

Hi,

A "bulk" calculation is for an "infinite" solid and thus even at infinity
there are atoms. So there is no chance to obtain what you are looking for
from the bulk.

The only way to do this is by a simulation of a "surface-slab" with some
(as thick as possible) vacuum between the slabs (which should also be as
thick as possible).
Realistically, this depends on your sample, but maybe even 7 layers of
bulk will do it, seperated by 30 bohr of vaccum. The potential in the
middle of the vacuum (printed in the scf file) could serve as your
"reference potential" at "infinity".

> I know that Wien references all calculated energy levels to the average
> lattice potential, but is there a way that I can obtain this average lattice
> potential relative to the lattice continuum threshhold (the potential at
> infinite distance from the crystal plus the surface potential barrier).  I am
> probably not explaining this well, so I will elaborate by giving an example of
> why I want this information.  Suppose I have a lattice for which I have
> calculated the band structure using Wien and I want to compare this
> bandstructure to the atomic energy levels of a dopant atom (which are
> calculated relative to the potential at infinite distance from the atom using
> a package such as Gaussian).  In order to make this comparison, I need to
> shift the lattice energy levels by an appropriate amount so that they have the
> same reference as the atomic levels.  How do I get the value for the energy
> shift?  Thanks.
> 
> Craig Plaisance
> Louisiana State University
> Baton Rouge, LA
> 
> _______________________________________________
> Wien mailing list
> Wien at zeus.theochem.tuwien.ac.at
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> 


                                      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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