[Pw_forum] How to consider finite system 's deformation with PW method?

[Nicola Marzari]

lan haiping wrote:
> Dear Stefano ,
> Sorry for my misexpression of my previous question.
> What i really want to ask is  whether  QE can deal with dynamical 
> properties of finite system under  certain condition such 
> as external  pressure .
> For  periodic crystal system,  as far as i know, QE can perform 
> calculation under external hystrostatic pressure. For single system such 
> as nanotube with supercell, does this external hystrostatic pressure 
> scheme still hold ?
>  
> Regards,
>  
> Hai-Ping


Dear Hai-Ping,

to apply pressure on an extended/bulk system you usually squeeze the
unit cell (Parrinello-Rahman, see PRL early '80s, or recent work with
Martonak and metadynamics).

For a finite systems, you squeeze a unit cell filled up with a
compressible medium (e.g. Martonak PRL 00), or, as recently proposed
by us (Cococcioni PRL 05) you use a modified electronic enthalphy
functional (The electronic enthalpy functional will soon appear
in CP).

In the meanwhile, you might want to look at the work of Tangney
on nanotubes under pressure.

All the best,

				nicola


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Prof Nicola Marzari   Department of Materials Science and Engineering
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