<div dir="ltr">thanks for your reply<br><br>
<div class="gmail_quote">2008/10/10 Stefano Baroni <span dir="ltr"><<a href="mailto:baroni@sissa.it">baroni@sissa.it</a>></span><br>
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<div>On Oct 10, 2008, at 3:58 AM, yumin qian wrote:</div><br>
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<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">There is one problem I am not clear about DFPT in external electronmagnetic field. How to switch on the external field since the field will distroy the translational symmetry(periodic boundary condition ).</blockquote>
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<div><br></div></div>please, take the time to have a glance at:</div>
<div>S. Baroni, S. de Gironcoli, A. Dal Corso, and P. Giannozzi, Phonons and related crystal properties from density-functional perturbation theory, Rev. Mod. Phys. 73, 515 (2001). </div>
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<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid"><span></span>There a two way right now : one is add a dipole layer in vaccum layers , this method can only be used in slab calculation </blockquote>
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<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid"><span></span>the other is to add a periodic field and at the end make the periodic to infinite (long wave appriximation). Vanderbilt also made a proposal using the Berry phase approach,</blockquote>
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<div><br></div></div>third, DFPT (restricted to the linear, or low-order) regime</div>
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<div class="gmail_quote"></div> My question is in PWSCF how the electronic field is added , </div></blockquote>
<div><br></div></div>through either of the first two methods. the third is implemented in PHONON</div>
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<div dir="ltr">and whether the method can be used in metal system ? </div></blockquote>
<div><br></div></div>homogeneous electric fields in a metal? for that a computer code is not enough. One should modify Maxwell's equations!</div>
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<div>SB</div>
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<div style="MARGIN: 0px"><font size="3"><span style="FONT-SIZE: 12px">---</span></font></div>
<div style="MARGIN: 0px"><font size="3"><span style="FONT-SIZE: 12px">Stefano Baroni - SISSA</span></font><font size="3"><span style="FONT-SIZE: 12px"> </span></font><font size="3"><span style="FONT-SIZE: 12px">&</span></font><font size="3"><span style="FONT-SIZE: 12px"> </span></font><font size="3"><span style="FONT-SIZE: 12px">DEMOCRITOS National Simulation Center - Trieste</span></font></div>
<div style="MARGIN: 0px"><font size="3"><span style="FONT-SIZE: 12px"><a href="http://www.sissa.it/~baroni" target="_blank">http://www.sissa.it/~baroni</a> / [+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype)</span></font></div>
<div style="FONT-SIZE: 12px; MIN-HEIGHT: 14px; MARGIN: 0px"><br style="FONT-SIZE: 12px"></div>
<div style="FONT-SIZE: 12px; MIN-HEIGHT: 14px; MARGIN: 0px"><span style="FONT-SIZE: 14px">
<div style="MARGIN: 0px"><font size="3"><span style="FONT-SIZE: 12px">La morale est une logique de l'action comme la logique est une morale de la pensée - Jean Piaget</span></font></div>
<div style="MARGIN: 0px"><font size="3"><span style="FONT-SIZE: 12px"><br></span></font></div></span></div>
<div style="MARGIN: 0px"><font size="3"><span style="FONT-SIZE: 12px">Please, if possible, don't</span></font><font size="3"><span style="FONT-SIZE: 12px"> </span></font><font size="3"><span style="FONT-SIZE: 12px">send me MS Word or PowerPoint attachments</span></font></div>
<div style="MARGIN: 0px"><font size="3"><span style="FONT-SIZE: 12px">Why? See:</span></font><font size="3"><span style="FONT-SIZE: 12px"> </span></font><font color="#0023e9" size="3"><span style="FONT-SIZE: 12px"><a href="http://www.gnu.org/philosophy/no-word-attachments.html" target="_blank">http://www.gnu.org/philosophy/no-word-attachments.html</a></span></font></div>
<div><font color="#0023e9" size="3"><span style="FONT-SIZE: 12px"><br></span></font></div></div></div></span><br></div></span><br></div></span><br></div></span><br></div><br></div><br>_______________________________________________<br>
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<br></blockquote></div><br><br clear="all"><br>-- <br>Sincerely Y. M. Qian <br>Lab.of Condensed Matter Theory and Materials Computation <br>Institute of Physics <br>Chinese Academy of Sciences<br>Tel: + 8610 8264 9147<br>
<a href="mailto:E-Mail%3Ayuminqian@gmail.com">E-Mail:yuminqian@gmail.com</a> <br>P.O.Box 603 Beijing 100190<br>China <br><br></div>