[Pw_forum] PBC problems

[Julen Larrucea]

yes, that is the amount of primitive cells.

Julen


On Mon, Dec 16, 2013 at 1:10 PM, 毛飞 <maofei at mail.bnu.edu.cn> wrote:

> Hi, Julen
>
>
>
> Hi, Julen
>
>
>
> Thank you for your immediate reply. I think you remarks are very usefully
> to me.
>
> I have another question about the PBC in bulk calculation. Sometimes the
> authors said, the PBC is used in their work, the supercell size (e.g. 4×4×4
> supercell) is chosen so as to minimize the spurious effects of the
> repetition.
>
>
>
> I wondering that what is meaning of 4, does it mean 4 primitive cells? And
> what is the relationship between the supercell and the simulation box.
>
>
>
> Thank you in advance.
>
> Evan
>
>
>
>
>
> -----原始邮件-----
> *发件人:* "Julen Larrucea" <julenlist at gmail.com>
> *发送时间:* 2013年12月16日 星期一
> *收件人:* "PWSCF Forum" <pw_forum at pwscf.org>
> *抄送:*
> *主题:* Re: [Pw_forum] PBC problems
>
>
>     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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>



-- 

-- 
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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