Dear Chris,
adding to my last reply: in the end, it all, of course, depends on what
you want to simulate. If you're aiming for a charged species on a surface
then assume_isolated='2D' might be wrong if you don't increase the slab
(mimicking the surface of a bulk material) such that the electric field
at the bottom does not influence the top. It might be worth to also look
at my implementation of a gate setup (gate=.true.) or to wait till the
author of assume_isolated='2D', Thibault Sohier, releases his implementation
including the gate setup. Gate? Maybe check this paper to see why this
could be useful:
https://www.sciencedirect.com/science/article/pii/S0169433218315022
As I said, it all depends on the situation you want to simulate. But a
flat potential with the same absolute value on both sides of the system
is rarely correct for a charged system.
Regards
Thomas
Zitat von Christoph Wolf <wolf.christoph@qns.science>:
Dear Thomas,
I played a bit with "assume_isolated='2D'" but I do not think that this can
correct the electrostatic potential of charged sytems (in the sense that
the potential becomes "flat") unless I am interpreting the output
(attached) wrong.
One way that gives me a flat vacuum potential is to use the M-P scheme but
that only works for cubic systems. After reading about the implementation
in VASP a bit I also think that is what they recommend.
Best,
Chris
On Thu, Jun 28, 2018 at 7:04 PM, Dr. Thomas Brumme <
thomas.bru...@uni-leipzig.de> wrote:
Dear Chris,
The potential shows the typical quadratic dependence on z since you're
calculating a charged system - there is a homogeneous background charge
since the 3D pbc system is assumed to be neutral. This has nothing to do
with the dipole correction. Depending on what you want to do next it might
be useful to set the flag assume_isolated='2D'
Regards
Thomas
Zitat von Christoph Wolf <wolf.christoph@qns.science>:
Dear all,
I am still observing something strange in my slab + dipole correction
calculation that I do not fully understand.
When using dipfield+tefield (eopreg and emaxpos well within the vacuum
region) I encounter a "saggy" electrostatic potential (plot_num=11)
despite
the sawtooth efield potential (plot_num=12) looking as usual. Maybe
someone
can give it a look and confirm if this is due to the excess charge in the
system (this does not happen when running the same system in VASP)?
I attach input and the plot of the potential for 2 and 4 layers of vacuum
(more vacuum does seem to improve the situation).
Thank you in advance for your time and assistance!
Chris
PS: I am using a QE version with dipole bug fix:
Program PWSCF v.6.2.2 starts on 25Jun2018 at 10:39:24
--
Postdoctoral Researcher
Center for Quantum Nanoscience, Institute for Basic Science
Ewha Womans University, Seoul, South Korea
--
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
--
Postdoctoral Researcher
Center for Quantum Nanoscience, Institute for Basic Science
Ewha Womans University, Seoul, South Korea
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