[Wien] Cu(111) Surface State

[Peter Blaha]

If you are interested on surface states, you MUST use a very thick slab
with lots of vacuum. Forget your 5 and 7-layer calculations. In these
models the 2 surfaces of the slab interact with each other and this leads
to a large splitting of the two surface states (there are 2 surface
states, because in our slab model we have two surfaces!) This interaction
can be via the slab or via the vacuum, so both parameters must be checked.

Your results are fine, when you see two (nearly) degenerate
bands, which are both the surface state, in your bandstructure plot.

Some shift in the position of the eigenvalues with respect to experiment
is "normal". This is the well known DFT problem.

PS: WIEN can obtain these image potential states, but your slab must be
appropriate. We can even quantitativel explain the splitting of the
surface state into two states in Au due to spin-orbit interactions, but
for your Cu this is irrelevant.

 > Dear all,
>   I was doing slab calculation for Cu(111). From experiments, there is
> a surface state 0.39eV below the Fermi energy. I did 5-layer, 7-layer,
> and 21-layer slabs (with 4, 8, and 8 layers of vaccum respectively).
> The calculated surface states are 0.3, 0.44, and 0.54 eV respectively.
> The charge convergence criterions are 0.01, 0.01, and 0.005 respectively.
> All 3 cases are calculated using the potential option PBE96. I am
> wondering if those calculated energies are the best Wien2k can do.
>   A previous question was discussed between Stolbov and Prof Blaha
> (in the "new digest", 2003 December, "Plotting surface potential").
> >From that It seems PBE96 is OK for Cu(111) surface potential.
>   On the other hand, on Phys Phys. Rev. B 195110-4 (2001) it says that
> wien97 cannot yield the asymptotic image potential so that the Cu(111)
> surface state turns out to be incorrect.
>   I am thinking if the suggestion of the above PRB paper applies to my
> case. Or, the image-potential problem has been fixed in Wien2k, the
> surface-state energies I calculated are off the experiment due to other
> technical problems.
>   I appreciate very much if anyone can give me suggestions.
>
> Chiung-Yuan
>
> _______________________________________________
> Wien mailing list
> Wien at zeus.theochem.tuwien.ac.at
> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>


                                      P.Blaha
--------------------------------------------------------------------------
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/
--------------------------------------------------------------------------