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 <[email protected]> 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 <[email protected] > 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. >> >> >> _______________________________________________ >> users mailing >> [email protected]https://lists.quantum-espresso.org/mailman/listinfo/users >> >> >> -- >> 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: [email protected] >> >> > -- > 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: [email protected] > >
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