[Pw_forum] adding vacuum
jaretqi at yahoo.com
Tue Nov 17 19:17:47 CET 2015
Pascal:Do not you think z-vector will shrink till it reaches the optimal length?
On Tuesday, November 17, 2015 12:35 AM, Pascal Boulet <pascal.boulet at univ-amu.fr> wrote:
So, I think in this case you should also relax the z-axis: The system tends to fill the vacuum by moving atoms since it cannot adapt the cell parameter.
Le 16 nov. 2015 à 21:49, Jaret Qi <jaretqi at yahoo.com> a écrit :
To make it clear, I am not adding vacuum to isolate my system like in graphene where we make the z-axis large enough to make it graphene not graphite. My system is a (001) interface between semi-metallic and semiconductor, so i am trying to minimize the interaction along the interface which is along the z-axis and study some properties and match it with experimental results. I need a reasonable vacuum so I began with 4A.
On Monday, November 16, 2015 1:31 PM, Nicola Marzari <nicola.marzari at epfl.ch> wrote:
On 16/11/2015 21:17, Jaret Qi wrote:
> but that will cost time!
you are right! just keep the 4 angstroms, no one will notice.
(actually, skip the calculations altogether, and make up some
plausible numbers in your paper - that will be even faster).
> On Monday, November 16, 2015 9:26 AM, Pascal Boulet
> <pascal.boulet at univ-amu.fr> wrote:
> 4 angstroms wide seems to be very small for the vacuum. As a rule of
> thumb you should use at least 2.5 times the thickness of your slab. This
> is what we observed in the calculations of semiconductor slabs. This has
> to be tested.
> Le 16 nov. 2015 à 16:40, Jaret Qi <jaretqi at yahoo.com
> <mailto:jaretqi at yahoo.com>> a écrit :
>> Hello all,
>> I am trying to minimize the interaction between my system and its
>> periodic images. To do so, I introduced a layer of vacuum along the
>> z-axis by increasing the lattice vector along the z-axis by 4A. At the
>> same time, I fixed it by using this parameter: cell_dofree='2Dxy',
>> But I have noticed atoms that are close to the vacuum move along the
>> z-axis and vacuum is decreasing, is this wrong or I should use
>> different cell_dofree?
>> note:relaxation still ongoing, not relaxed yet.
>> Pw_forum mailing list
>> Pw_forum at pwscf.org <mailto:Pw_forum at pwscf.org>
> Pascal Boulet /- MCF HDR, Resp. L1 MPCI - DEPARTEMENT CHIMIE/
> Aix-Marseille Université - ST JEROME - Avenue Escadrille Normandie
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Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL
Director, National Centre for Competence in Research NCCR MARVEL, EPFL
Pascal Boulet - MCF HDR, Resp. L1 MPCI - DEPARTEMENT CHIMIEAix-Marseille Université - ST JEROME - Avenue Escadrille Normandie Niemen - 13013 MarseilleTél: +33(0)4 13 55 18 10 - Fax : +33(0)4 13 55 18 50Site : http://allos.up.univ-mrs.fr/pascal - Email : pascal.boulet at univ-amu.frAfin de respecter l'environnement, merci de n'imprimer cet email que si nécessaire.
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