[Pw_forum] Au (111) Surface Energy

[Ari P Seitsonen]

Dear Jack Davis,

   It is well known in the community that this is not a very accurate 
approach to calculate the surface energy, even if in principle correct 
(or, even the definition): You should at least make sure that the bulk is 
calculated along the (111) direction with the same k point sampling. Only 
if you are very well converged with the k point sampling in both the slab 
and bulk you might get a converged value. A classic article discussing 
this problem is

Vincenzo Fiorentini and M Methfessel 1996 J. Phys.: Condens. Matter 8 6525 
doi:10.1088/0953-8984/8/36/005
"Extracting convergent surface energies from slab calculations"

   I can also try to find some more recent references if you wish.

     Greetings from Zurich,

        apsi

-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-
   Ari P Seitsonen / Ari.P.Seitsonen at iki.fi / http://www.iki.fi/~apsi/
   Physikalisch-Chemisches Institut der Universitaet Zuerich
   Tel: +41 44 63 54 497  /  Mobile: +41 79 71 90 935


On Fri, 15 Nov 2013, Jack Davis wrote:

> Dear Forum,
>
> I’m trying to calculate surface energies using PWscf, however, I am unsure of the methodology. To begin with we calculate the bulk energy of the FCC unit cell, using the attached input. We then calculate the energy of a 111 slab, 10 layers thick with a 6 atom vacuum gap. The surface energy is then calculated as,
>
> Surface energy = Energy of slab - (bulk energy * 10) / 2.
>
> I think I am probably misunderstanding the energies PWscf is giving me. We’re getting some strange answers!
>
> Thank you,
> Jack Davis
>
> School of Chemistry
> University of Birmingham
>