[Pw_forum] adding vacuum

[Axel Kohlmeyer]

On Mon, Nov 16, 2015 at 3:30 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).

right! after all, we already know that the answer to the ultimate
question about life, the universe and everything is 42.  ;-)

axel.


>
>                         nicola
>
>>
>>
>>
>> On Monday, November 16, 2015 9:26 AM, Pascal Boulet
>> <pascal.boulet at univ-amu.fr> wrote:
>>
>>
>> Hello,
>>
>> 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.
>>
>> Pascal
>>
>> 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.
>>>
>>>
>>> JARET,
>>> ASU
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>>
>> --
>> Pascal Boulet /- MCF HDR, Resp. L1 MPCI - DEPARTEMENT CHIMIE/
>> Aix-Marseille Université - ST JEROME - Avenue Escadrille Normandie
>> Niemen - 13013 Marseille
>> Tél: +33(0)4 13 55 18 10 - Fax : +33(0)4 13 55 18 50
>> Site : http://allos.up.univ-mrs.fr/pascal - Email :
>> pascal.boulet at univ-amu.fr <mailto:pascal.boulet at univ-amu.fr>
>> /Afin de respecter l'environnement, merci de n'imprimer cet email que si
>> nécessaire./
>>
>>
>>
>>
>>
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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
> http://theossrv1.epfl.ch/Main/Contact http://nccr-marvel.ch/en/project
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-- 
Dr. Axel Kohlmeyer  akohlmey at gmail.com  http://goo.gl/1wk0
College of Science & Technology, Temple University, Philadelphia PA, USA
International Centre for Theoretical Physics, Trieste. Italy.