Both methods should give the same result - they did at least when I
tried. But you can't calculate phonons with dipole correction so if
you want those start with assume_isolated = '2D'
But read all infos given in input_pw and the related papers - it helps
to understand how to setup the system ;)
Thomas
Zitat von Asad Mahmood <amahm...@phys.qau.edu.pk>:
Thank you Thomas, I will try both flag one by one and see what change do
each of them brings separately.
On Tue, Nov 13, 2018 at 3:52 PM Thomas Brumme <thomas.bru...@uni-leipzig.de>
wrote:
Dear Asad,
please also answer to the list ;) ("reply all")
No! It's either dipfield = .true. or assume_isolated ='2d'. If you want to
simulate "a real" 2D system using
the Coulomb cutoff you don't need to correct due to the systems dipole.
And if you correct with the artificial
dipole, cutting of the Coulomb will result in something bad/weird...
Actually, I don't know if this will work at all.
So, either dipfield = .true. or assume_isolated ='2d'
Thomas
On 11/13/18 11:45, Asad Mahmood wrote:
Thanks Thomas for reply. So I need to include both flags(i.e dipfielf =
.true and assume_isolated ='2d' ) in relax or structure optimization
calcations ?
On Tue, Nov 13, 2018, 3:11 PM Thomas Brumme <thomas.bru...@uni-leipzig.de
wrote:
Dear Asad,
What is the benefit of using dipfield=.true.? Well, the benefit is that
you get the correct electronic structure,
energetics, and so on. As you want to simulate a 2D system with 3D
boundary conditions this is the only
correct way if you have an asymmetric system (in the z-direction,
assuming the 2D system is in xy). Well,
not the only correct way. Recently a Coulomb cutoff technique was
implemented in QE, check input flag
assume_isolated='2D'
Regards
Thomas
P.S.: If you have a dipole in your system you'll see that properties
(especially the total energy) will change
with increasing vacuum region. If you increase it, you'll minimize the
eigenfunction overlap between the
repeated layers but the Coulomb interaction will never be zero and thus
you can get wrong results - and
this will be worse for larger dipole, e.g., the flourinated graphene.
On 11/13/18 08:38, Asad Mahmood wrote:
Hi,
I have a hexagonal graphene(or any other) monolayer and I hydrogenate(or
flourinate, etc.) on the top surface only (single sided). Is there need to
use flag dipfield = .true ? What is benefit or disadvantage of using this
flag for optimization of L.C or bond length?
I am using 20 angstrom vacuum between two layers to avoid mutual
influence.
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--
Dr. rer. nat. Thomas Brumme
Wilhelm-Ostwald-Institute for Physical and Theoretical Chemistry
Leipzig University
Phillipp-Rosenthal-Strasse 31
04103 Leipzig
Tel: +49 (0)341 97 36456
email: thomas.bru...@uni-leipzig.de
--
Dr. rer. nat. Thomas Brumme
Wilhelm-Ostwald-Institute for Physical and Theoretical Chemistry
Leipzig University
Phillipp-Rosenthal-Strasse 31
04103 Leipzig
Tel: +49 (0)341 97 36456
email: thomas.bru...@uni-leipzig.de
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