[Pw_forum] cut-off energy doesnt optimized

[Francesco Pelizza]

As far as I am concerned you cannot expect better accuracy than 0.001 Ry 
and it must be applied to the number of atoms within your box.

So if you have 8 atoms, the convergence will be optimised after hvaing a 
variation of less than 0.008 Ry between a scf with N cutoff and its next 
increment.

There are tutorials on QE website that explain it


Francesco Pelizza




On 05/05/17 12:16, project way wrote:
> Dear QE users
>
> I am running ZnO bulk scf for different cut-off energy but Etot didnt 
> optimized.
>
> Ecut= 40  Etot=-317.466 Ry
> Ecut= 50  Etot=-317.484 Ry
> Ecut= 60  Etot=-317.492 Ry
> Ecut= 75  Etot=-317.493 Ry
>
> for optimization with 0.0001  i should increase Ecut too much?
>
>
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