[Pw_forum] Fwd: vc-relax optimization of the atomic structure

[Matic Poberznik]

Dear Ali,

please before posting to the forum read these guidelines:

http://www.quantum-espresso.org/forum/#1.0

> hello
> i want to calculation vc-relax quantum dots MAPbBr3 . how do i choose
> ecutoff for QDS 2.5 nm .i have chosen ecutoff 30 ry for bulk MAPbBr3
> so how do i choose ecutoff for QDS 2.5 nm
> thank you.
> 

If you want to compare results the same cutoff must be used in all
calculations, but it shouldn't be determined randomly. You should check
the convergence with respect to the pseudopotentials you are using, If
you are using ultrasoft pseudopotentials typically ecutrho must be
increased as well. Here is an example of how to test convergance:

www.tcl.t.u-tokyo.ac.jp/pdf/2014_lm/1st_day_pm.pdf

I suggest that you do more "google" research and then post a more
specific query to this forum if you encounter any issues.

Best Regards,

Matic Poberznik
-- 
Matic Poberznik
J. Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia