[Pw_forum] [100] surface relaxation of Al

[Denis Davydov]

Dear Prof. Marzari,

Thanks for your reply.  I will use the sampling you suggested. 

With regards to "right/wrong", after some literature review i would say the results are rather correct. 
The interlayer distance change during surface relaxation 
could indeed be non-monotonous, as was shown, for example, here

Huang, G. (2008). Electronic structures, surface phonons, and electron-phonon interactions of Al(100) and Al(111) thin films from density functional perturbation theory. Physical Review B, 78(21), 214514. doi:10.1103/PhysRevB.78.214514

In any case, i will play more with this simple toy-problem.

Sincerely,
Denis 

On 06.05.2013, at 19:25, Nicola Marzari <nicola.marzari at epfl.ch> wrote:

> 
> 
> Hi Denis,
> 
> not sure anything looks wrong, a part that your smearing is quite small,
> and you might want to test that and the k-points used.
> 
> In any case, you could try to leave all atoms free to relax, and study interlayer relaxations as a function of thickness, and see how the outer
> interlayer relaxations converge to their true value as a function of thickness (and progressively the inner relaxations as well).
> 
> Last - no need to sampe in the x direction - your system
> should not have any band dispersion there (if it has, there is not
> enough vacuum).
> 
> Hence, 1 16 16 0 1 1 is a very good sampling (even 1 8 8 0 1 1 would
> be great, provided you use maybe a more reasonable smearing of .01-.02).
> 
> 
> 				nicola