Dear Stefano,<br>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.<br>Thank you<br><br>Regards<br>Hai-Ping
<br><br><br><div><span class="gmail_quote">On 9/19/07, <b class="gmail_sendername">degironc</b> <<a href="mailto:degironc@sissa.it">degironc@sissa.it</a>> wrote:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
the static dielectric constant of a metal is infinit....<br>what are you trying to calculate ?<br>stefano<br><br>lan haiping wrote:<br>> Thank you, Prof Marzari.<br>><br>> As far as i know, the changes of the WFs' centers can be applied to
<br>> insulating systems.<br>> While for metallic or semi-metallic systems, Is such scheme still<br>> useful ? in fact, i still donot know how to define the wfs' centers<br>> for metallic systems.<br>>
<br>> i found it is hard to achieve convergence when i applied<br>> electric-enthalpy approache to<br>> metallic systems no matter which direction of the uniform electric<br>> field involves.<br>> i do notice the difficulties of scf convergence of systems under
<br>> electric field. i tried to<br>> reduce mixing parameter , or increase the smearing width, but no<br>> success. Are there<br>> any other parameters i should pay attention to ?<br>><br>> With Regards,
<br>> Hai-Ping<br>><br>><br>> On 9/19/07, *Nicola Marzari* <<a href="mailto:marzari@mit.edu">marzari@mit.edu</a><br>> <mailto:<a href="mailto:marzari@mit.edu">marzari@mit.edu</a>>> wrote:<br>>
<br>><br>><br>> Dear Hai-Ping,<br>><br>> it was done directly with real space integration - i.e. in the<br>> transferse direction, the dipole is given by the integral of r rho(r).<br>><br>
> It could also be done by looking at the change in position of the<br>> sum of the centers of the Wannier functions - this is less accurate,<br>> since the reciprocal-space expression for the position operator is
<br>> based on a finite-differences discretization.<br>><br>><br>> nicols<br>><br>><br>> lan haiping wrote:<br>> > Hi, All.<br>> > I have read a work of Prof Marzari performed by QE package to
<br>> > compute static dielectric properties of nanotube systems : PRL<br>> 96, 166801.<br>> > To extract dielectric quantities, there are 2 methods<br>> mentioned in<br>> > this work. I have a question about the method adopted by the
<br>> sawtooth<br>> > potential . In order to obtain transverse polarizability , we<br>> need know<br>> > the dipole moment induced by external sawtooth potential . I<br>> have done
<br>> > several tests on similar systems carbon nanotube (6,0), but i<br>> have not<br>> > found how to extract such induced dipole moment .<br>> > Would anyone please give me a hand on this subject ? Any
<br>> tips or<br>> > references are appreciated !<br>> ><br>> > Best wishes<br>> > Hai-Ping<br>> ><br>><br>> --<br>> ---------------------------------------------------------------------
<br>> Prof Nicola Marzari Department of Materials Science and Engineering<br>> 13-5066 MIT 77 Massachusetts Avenue Cambridge MA 02139-4307 USA<br>> tel 617.4522758 fax 2586534 <a href="mailto:marzari@mit.edu">
marzari@mit.edu</a><br>> <mailto:<a href="mailto:marzari@mit.edu">marzari@mit.edu</a>> <a href="http://quasiamore.mit.edu">http://quasiamore.mit.edu</a><br>> _______________________________________________
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http://www.democritos.it/mailman/listinfo/pw_forum</a><br>><br>><br>><br>><br>> --<br>> Hai-Ping Lan<br>> Department of Electronics ,<br>> Peking University , Bejing, 100871<br>> <a href="mailto:lanhaiping@gmail.com">
lanhaiping@gmail.com</a> <mailto:<a href="mailto:lanhaiping@gmail.com">lanhaiping@gmail.com</a>>, <a href="mailto:hplan@pku.edu.cn">hplan@pku.edu.cn</a><br>> <mailto:<a href="mailto:hplan@pku.edu.cn">hplan@pku.edu.cn
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<br>-- <br>Hai-Ping Lan <br>Department of Electronics ,<br>Peking University , Bejing, 100871<br><a href="mailto:lanhaiping@gmail.com">lanhaiping@gmail.com</a>, <a href="mailto:hplan@pku.edu.cn">hplan@pku.edu.cn</a>