[Pw_forum] Monolayer WSe2 related problems

[Thomas Brumme]

Dear Anindya Bose,

it seems that you need to go back to the basics and try to understand 
some things.
And if someone of your group would help, it would be much better also 
for you.
+ Sometimes one just needs to read the publications corresponding to a 
method.

The cutoff for the wave functions has nothing to do with whether you 
want to simulate
a monolayer or a bulk system - the cutoff depends on the pseudopotential 
you're using.

Whether to use esm_bc or just adding vacuum cannot be answered without 
knowing
what you want to do afterwards. Both methods should give the same result 
if you're
calculating an uncharged system - in fact, the esm method also needs to 
use some
vacuum to avoid interactions between the repeated images (via 
overlapping wave
functions). Read the paper by Otani/Sugino in order to understand the 
method:

http://journals.aps.org/prb/abstract/10.1103/PhysRevB.73.115407

Without knowing what you mean with "I am getting convergence problems" 
we cannot
help.

Thomas


On 03/09/2017 08:32 AM, Anindya Bose wrote:
> Dear Sir,
> To simulate a isolated Monolayer WSe2 structure(nat=3,ntyp=2) , should 
> I choose the value of ecutwfc very high(=70, ecutrho=4*ecutwfc) and 
> should I use esm_bc to add vacuum or should I increase this using 
> stretch cell method.Actually I am getting convergence problems.Please 
> tell me how to sort this out.
>
> Thanks and regards,
> Anindya Bose
>
>
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-- 
Dr. rer. nat. Thomas Brumme
Max Planck Institute for the Structure and Dynamics of Matter
Luruper Chaussee 149
22761 Hamburg

Tel:  +49 (0)40 8998 6557

email: Thomas.Brumme at mpsd.mpg.de

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