[Pw_forum] problem with TPSS (Tao-Perdew-Staroverov-Scuseria) meta-GGA for silicon

[Gabriele Sclauzero]

Ari P Seitsonen wrote:
> 
> Dear Rafael,
> 
>   Adding to Axel's comment; you might experience the problem of 
> "non-spherical" atom in Si since in the free atom you have two 
> p-electrons to put on three degenerate (spin-up) states. Thus there will 
> be a fight (= usually no convergence) which one of p_x, p_y and p_z will 
> get them if tried straightforwardly. What one can try is to modify the 
> cell slightly making it non-cubic, 

This solution is nice, I'll try it someday. Anyway, the pw.x flag:

nosym=.true.

could do the job in this case (and it is often useful for computing atoms or molecules in 
supercells).
You can even fix occupations in the more problematic cases, by setting:

occupations = 'from_input'

and specifying the desired occupations at the end of the namelists.

NB: works only with gamma point

Hope this helps,

regards

GS

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