[Pw_forum] Graphene on BN : unable to reach convergence

[Gabriele Sclauzero]

mohamed sabri majdoub wrote:
> Dear Jess,
> 
> Thank you for your response.
> Could you elaborate please more by my ecut/ecutwfc are not correct 
> because I am using norm conserving pseudos.
> I am a beginner with pwscf. 

You can start having a look at lecture slides and sample files from hands on sessions 
available online here:

http://media.quantum-espresso.org/santa_barbara_2009_07/index.php


> How would I know which values of ecutwfc I 
> should use?

Testing for convergence of total energy and other quantities of your interest 
(magnetization for instance), by increasing the cutoff ecutwfc and monitoring the behavior 
of those quantities.

> In case I would change pseudo type what I should do?

Download the file, put in pseudo_dir and change your input file accordingly. Test again 
for convergence.

Normconserving pseudopotentials always need ecutrho=4*ecutwfc (which is the default, so 
that you should not specify a value for it), while ultrasoft need ecutrho > 4*ecutwfc 
(usually ecutrho ~ 8*ecutwfc or bigger).


Regards,


Gabriele

> Thank you again for your help.
> 
> 

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