[Pw_forum] How to choose ecutwfc value?

Nicola Marzari nicola.marzari at epfl.ch
Sat Oct 7 12:39:55 CEST 2017

Dear Saif,

At the link below you find suggested pseudos and cutoffs - 30Ry for Li 
and Na, 50Ry for Cl try adsorption energies at 30, 40 and 50 Ry, first 
keeping the same geometry in all calculations, then relaxing everything. 
Please send to the forum a report with these 6 numbers, and those from
SIESTA, Gaussian, and VASP.



On 07/10/2017 02:28, Saif Ullah wrote:
> 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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Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL
Director, National Centre for Competence in Research NCCR MARVEL, EPFL
http://theossrv1.epfl.ch/Main/Contact http://nccr-marvel.ch/en/project

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