[Pw_forum] ncpp for Ag

[Lorenzo Paulatto]

In data 15 luglio 2009 alle ore 10:45:12, ambavale sagar  
<sagarambavale at yahoo.co.in> ha scritto:
> If I use uspp along with ncpp in the calculations, which would be  
> changes in the values of ecut and ecutrho?

It depends on the details of the various pseudopotentials, it is likely  
that one of the norm-conserving will require the higher ecutwfc (and that  
values will have to be used for all the calculations). Under this  
assumption, you have to test the ultrasoft pseudopotential with this high  
values of ecutwfc and test if it is well converged with respect to ecutrho.

Let's make an example, "->" means "is well converged at":
S -> ecutwfc = 50Ry
C -> ecutwfc = 60Ry
H -> ecutwfc = 45Ry

=> you'll have to take ecutwfc=60, which imply ecutrho >= 60*4 = 240

case 1:
Ag -> ecutwfc = 25, ecutrho = 200
==> you just take ecutwfc=60, and ecutrho will be large enough for the Ag  
pseudopotential too

case 2:
Ag -> ecutwfc = 36, ecutrho = 360
==> you have to take ecutwfc=60 (as required by the C pseudopotential) and  
ecutrho=360 (as required by the Ag ultrasoft-pseudopotential)

best regards


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Lorenzo Paulatto
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