[Pw_forum] Question about induced dipole moment

[lan haiping]

Dear Stefano,
i notice such problem, but in Prof Marzari's work on cnt, the transverse
polarizabilities of metallic nanotubes are given.  My confusion may be due
to this example.
Thank you

Regards
Hai-Ping


On 9/19/07, degironc <degironc at sissa.it> wrote:
>
> the static dielectric constant of a metal is infinit....
> what are you trying to calculate ?
> stefano
>
> lan haiping wrote:
> > Thank you, Prof Marzari.
> >
> > As far as i know, the changes of the WFs' centers can be applied to
> > insulating systems.
> > While for metallic or semi-metallic systems, Is such scheme still
> > useful ?  in fact, i still  donot know how to define the wfs' centers
> > for metallic systems.
> >
> > i found it is hard to achieve convergence when i applied
> > electric-enthalpy approache to
> > metallic systems no matter which direction of the uniform electric
> > field involves.
> > i do notice the difficulties of scf convergence  of systems under
> > electric field.  i tried to
> > reduce mixing parameter , or increase the smearing width, but no
> > success.   Are there
> > any other parameters i should pay attention to ?
> >
> > With Regards,
> > Hai-Ping
> >
> >
> > On 9/19/07, *Nicola Marzari* <marzari at mit.edu
> > <mailto:marzari at mit.edu>> wrote:
> >
> >
> >
> >     Dear Hai-Ping,
> >
> >     it was done directly with real space integration - i.e. in the
> >     transferse direction, the dipole is given by the integral of r
> rho(r).
> >
> >     It could also be done by looking at the change in position of the
> >     sum of the centers of the Wannier functions - this is less accurate,
> >     since the reciprocal-space expression for the position operator is
> >     based on a finite-differences discretization.
> >
> >
> >                                     nicols
> >
> >
> >     lan haiping wrote:
> >     > Hi,   All.
> >     >     I have read a work of  Prof Marzari  performed by QE package
> to
> >     > compute static dielectric properties of nanotube systems : PRL
> >     96, 166801.
> >     >      To extract dielectric quantities, there are 2 methods
> >     mentioned in
> >     > this work. I have a question about the method adopted by the
> >     sawtooth
> >     > potential . In order to obtain transverse polarizability , we
> >     need know
> >     > the  dipole moment induced by external sawtooth potential .  I
> >     have done
> >     > several tests on similar systems carbon nanotube (6,0), but i
> >     have not
> >     > found how to extract such induced dipole moment .
> >     >  Would anyone please give me a hand on this subject  ?    Any
> >     tips or
> >     > references  are appreciated !
> >     >
> >     >    Best wishes
> >     >     Hai-Ping
> >     >
> >
> >     --
> >
> ---------------------------------------------------------------------
> >     Prof Nicola Marzari   Department of Materials Science and
> Engineering
> >     13-5066   MIT   77 Massachusetts Avenue   Cambridge MA 02139-4307
> USA
> >     tel 617.4522758 fax 2586534 marzari at mit.edu
> >     <mailto:marzari at mit.edu> http://quasiamore.mit.edu
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> >
> >
> >
> >
> > --
> > Hai-Ping Lan
> > Department of Electronics ,
> > Peking University , Bejing, 100871
> > lanhaiping at gmail.com <mailto:lanhaiping at gmail.com>, hplan at pku.edu.cn
> > <mailto:hplan at pku.edu.cn>
> > ------------------------------------------------------------------------
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-- 
Hai-Ping Lan
Department of Electronics ,
Peking University , Bejing, 100871
lanhaiping at gmail.com, hplan at pku.edu.cn
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