Thank you, Prof Marzari.<br><br>As far as i know, the changes of the WFs' centers can be applied to insulating systems.<br>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.
<br> <br>i found it is hard to achieve convergence when i applied electric-enthalpy approache to <br>metallic systems no matter which direction of the uniform electric field involves. <br>i do notice the difficulties of scf convergence of systems under electric field. i tried to
<br>reduce mixing parameter , or increase the smearing width, but no success. Are there <br>any other parameters i should pay attention to ? <br><br>With Regards,<br>Hai-Ping<br><br><br><div><span class="gmail_quote">On 9/19/07,
<b class="gmail_sendername">Nicola Marzari</b> <<a href="mailto:marzari@mit.edu">marzari@mit.edu</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;">
<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 96, 166801.<br>> To extract dielectric quantities, there are 2 methods mentioned in
<br>> this work. I have a question about the method adopted by the sawtooth<br>> potential . In order to obtain transverse polarizability , we need know<br>> the dipole moment induced by external sawtooth potential . I have done
<br>> several tests on similar systems carbon nanotube (6,0), but i have not<br>> found how to extract such induced dipole moment .<br>> Would anyone please give me a hand on this subject ? Any 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
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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>