[Pw_forum] Question about induced dipole moment

Nicola Marzari marzari at MIT.EDU
Tue Sep 18 22:30:06 CEST 2007

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.


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 http://quasiamore.mit.edu

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