[QE-users] N2 adsorption on Na surface

[Giuseppe Mattioli]

Dear Federico
On the top on Kazume's suggestions, I see that you are using an ONCV  
pseudopotential fo N. In my experience, it should require ecutwfc=90  
Ry (and ecutrho=360 Ry but you are already there) for proper  
convergence and your ecutwfc is much lower. It is so low to justify,  
alone, an awful description of N2.
Maybe you can try to use a more complete basis set and see if you  
obtain what you expect.
HTH
Giuseppe

Quoting Kazume NISHIDATE <nisidate at iwate-u.ac.jp>:

> Dear Federico
>
> You specify the option assume_isolated = '2D' to truncate the
> periodic Coulomb interaction along the c axis. However, your structure
> may need to be revised for this purpose.
>
> I think you need to shift all of the atomic positions upward by 7.5 A,
> half of the vacuum gap (15 A) so that the center of the vacuum region
> will be at the boundary.
>
> Also, in general, it is not necessary to put the N2 molecule on both
> sides of the slab if you securely truncate the Coulomb interaction over
> the cyclic boundary.
>
> Before you proceed, you should check the potential distribution along
> the c-axis which can be done by pp.x (plot_num=11) and average it in
> the xy plane with the average.x.
>
> Also, the bond length of the molecule may be different from its isolated
> neutral state if there is a significant charge transfer between the
> molecule and the surface.
>
> Good luck.
>
> Sincerely,
> Kazume



GIUSEPPE MATTIOLI
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