Dear Thomas, thank you for your detailed replies which were, as always, very helpful!
Best, Chris On Mon, Jul 2, 2018 at 2:57 PM, Dr. Thomas Brumme < thomas.bru...@uni-leipzig.de> wrote: > 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 >> > > > > -- Postdoctoral Researcher Center for Quantum Nanoscience, Institute for Basic Science Ewha Womans University, Seoul, South Korea
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