[Pw_forum] ncpp for Ag
Lorenzo Paulatto
paulatto at sissa.it
Wed Jul 15 12:10:46 CEST 2009
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
--
Lorenzo Paulatto
SISSA & DEMOCRITOS (Trieste)
phone: +39 040 3787 511
skype: paulatz
www: http://people.sissa.it/~paulatto/
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