[gpaw-users] LCAO calculations on metallic slabs

[Ask Hjorth Larsen]

Hi

On Fri, 30 Sep 2011, Ulrik Grønbjerg wrote:

> Dear fellow GPAW users,
> I would like to do calculations on slab containing Pt and Ca, but I
> encounter two, probably related, problems. First of all, the energies are
> obviously wrong, with total energies of +100 eV for the slab, in contrast to
> -350 eV that I get from regular GPAw calculations. The other problem is that
> the LCAO calculation will often fail in finding the Fermi level at some
> point. I have attached the script setting up the system, and the script I
> use to run the LCAO calculations.
> 
> I am not especially familiar with LCAO calculations, so I might very well be
> missing something basic, and any help will be greatly appreciated.
> 
> Best regards,
> Ulrik Grønbjerg Andersen

I think the crazy energies in the beginning have to do with the ordering 
of states defined in the PAW setup being different from that defined among 
the basis sets, resulting in bad initial occupations which however should 
be rectified during the SCF cycle.  This is something I'll probably have 
time to fix in November.  It happens whenever the same angular momentum 
channel is present more than once on a given PAW setup (so also for the 
standard setups for K, Ti, ...).

And thanks, Lasse, for figuring out a solution.

The FermiDirac occupations object also has a maxiter parameter which can 
be raised, although that should not be necessary under normal 
circumstances.

Regards
Ask