[Pw_forum] the problem of scf convergence

[Stefano Baroni]

Dear unnamed friend:
system? input file? name? affiliation?
thanks - Stefano Baroni

On Sep 13, 2007, at 6:23 AM, hyello25 Qgrui wrote:

> hello, everyone.
>   These days, I performed the convergence of scf calculation with  
> some USPP, but never see a good ecut convergence. The system only  
> contains 3 atoms, with 12x12x12 kpoints automatic generated in MP  
> grids.
>   Why does the press differ each so mush? Is 200ev Ry too high for  
> USPP? And which press is more convictional?
>   Can anyone give me some suggestion? Thanks in advance.
>  ecut=80 :
> !    total energy              =   -61.89999202 Ry
>           total   stress  (Ry/bohr**3)                   (kbar)      
> P=    0.59
>  ecut=100 :
> !    total energy              =   -61.90651146 Ry
>           total   stress  (Ry/bohr**3)                   (kbar)      
> P=   -5.39
>  ecut=140 :
> !    total energy              =   -61.90331161 Ry
>           total   stress  (Ry/bo hr**3)                    
> (kbar)     P=    0.97
>  ecut=180 :
> !    total energy              =   -61.90482904 Ry
>           total   stress  (Ry/bohr**3)                   (kbar)      
> P=   10.64
>  ecut=200 :
> !    total energy              =   -61.90542701 Ry
>           total   stress  (Ry/bohr**3)                   (kbar)      
> P=   -4.55
>  ecut=240 :
> !    total energy              =   -61.90875043 Ry
>           total   stress  (Ry/bohr**3)                   (kbar)      
> P=    5.92
>  ecut=280 :
> !    total energy              =   -61.90854533 Ry
>           total   stress  (Ry/bohr**3)                   (kbar)      
> P=    1.68
>
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---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center -  
Trieste
[+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype)

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