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Unless Zahra wanted to know how to obtain phonons from the electronic structure calculate by sampling only the gamma point of the Brillouin zone (BZ). Beware that the k-points used to sample the BZ (which i like to call "k points") have nothing to do with the k-points at which phonon frequencies are calculated (which I like to call "q points"). If you quant to calculate phonons at q-point=gamma, then please follow the suggestions by Giovanni Cantele and Stefano de Gironcoli. Otherwise, please make sure that you understand the difference between "k points" and "q points" (see my sloppy definition above). If you don't, please revert to us before proceeding. Good luck - SB<div><br><div><div>On Oct 29, 2007, at 9:21 PM, Giovanni Cantele wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">zahra sadat naghavi wrote:</div> <blockquote type="cite"><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">what should i do if i want to calculat phonon frequencies at gama<span class="Apple-converted-space"> </span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">point for a metal?</div> </blockquote><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">perhaps it could be helpful starting browsing the code documentation and<span class="Apple-converted-space"> </span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">examples:</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><a href="http://www.quantum-espresso.org/wiki/index.php/Using_PWscf#Phonon_calculations">http://www.quantum-espresso.org/wiki/index.php/Using_PWscf#Phonon_calculations</a></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">espresso-3.2/examples/example02</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">example 02 shows you "how to use pw.x and ph.x to calculate phonon</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">frequencies at Gamma and X for Si and C in the diamond structure and</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">for fcc-Ni."</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Giovanni</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">--<span class="Apple-converted-space"> </span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Dr. Giovanni Cantele</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Coherentia CNR-INFM and Dipartimento di Scienze Fisiche</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Universita' di Napoli "Federico II"</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Complesso Universitario di Monte S. Angelo - Ed. 6</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Via Cintia, I-80126, Napoli, Italy</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Phone: +39 081 676910</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Fax: <span class="Apple-converted-space"> </span>+39 081 676346</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">E-mail: <a href="mailto:Giovanni.Cantele@na.infn.it">Giovanni.Cantele@na.infn.it</a></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Web: <a href="http://people.na.infn.it/~cantele">http://people.na.infn.it/~cantele</a></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">_______________________________________________</div><div style="margin-top: 0px; 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