[Pw_forum] PBC problems

[Julen Larrucea]

Dear Evan,

leaving distance between a molecule and the boundary is normally used only
for simulating isolated molecules, or surfaces (in order to simulate the
vacuum on one of the sides of the crystal).

The point in using PBC in bulk, is that you can simulate an infinite system
by only computing a few atoms, and therefore there should not be any gap at
all.

A quick tip: you can use for example JMol for opening your pw.x output, and
then in the terminal type:
open "pw_output_file" {3 3 3}

This will show you 3 replicas of your system on each direction, and if you
want to simulate bulk, it should look uniform.

  Best regards

   Julen


On Mon, Dec 16, 2013 at 12:00 PM, 毛飞 <maofei at mail.bnu.edu.cn> wrote:

>
> Dear all
>
>
>
> I have a general question about doing calculation with periodic boundary
> condition (PBC). When I simulate the bulk materials (e.g. crystals), if I
> have applied the PBC in 3 dimensions of the simulation box, do I have to
> give some margins between the considered system and the boundary of the
> simulation box? Or there should be no space between them, the system should
> connected with its images seamlessly. But usually, as said in some papers,
> in order the minimize the spurious interaction with its images, the
> distance between the considered system and the boundary of the simulation
> box should be large enough.
>
>
>
> I am a little puzzled with this issue. Any comment is appreciated. Thank
> you in advance.
>
>
>
> Evan
>
>
>
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>



-- 

-- 
Dr. Julen Larrucea
Postdoctoral researcher,
BCCMS, HMI Group, University of Bremen
Phone: +49 421 218 64582
Fax: +49 421 218 64599
 http://www.larrucea.eu
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