[Pw_forum] How to choose ecutwfc value?

[Saif Ullah]

Dear qe users,

I'm a qe beginner, therefore, came up with a simple question. If i have to
study the interaction of Li/Na with graphene, so in this case how will i
choose the ecutwfc value? Should i do a convergence test w.r.t ecutwfc for
pure graphene or I must check the convergence of Li adsorbed graphene and
Na adsorbed graphene separately? For my pristine graphene, I found the 40Ry
value to be enough to converge graphene but when I studied the Li
interaction, my calculated adsorption value was very much underestimated
from my SIESTA/Gaussian/VASP values. Finally, I checked the convergence of
ecutwfc of Li/Na adsorbed graphene and found that 110Ry value is better for
both the Na and Li. This being said that an enormous increase in
computational time. I have seen a paper in which the authors used 30Ry and
reported the accurate results. My question is, the 110Ry is ok for Li/Na
graphene systems or I have done a mistake? Thanks in advance

Saif
Department of physics, ufjf, Brazil

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