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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Hi Umesh,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">If you are interested in sorting overlapping phonon branches so that you can plot them, then you need to sort them at each q point based on the phonon eigenvector
like Stefano noted. You can find this in the output from the matdyn calculation.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Keith Refson developed a script to sort phonon branches and plot them correctly based on eigenvectors for DFPT phonon calculations using CASTEP. Overrall, it
does a very good job. I wrote a small script that converts the QE output to the CASTEP format. If you are interested, I can send you a copy of the codes.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Best regards,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Derek<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#1F497D">Derek Stewart<o:p></o:p></span></b></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#1F497D">Principal Research Scientist<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#1F497D">HGST, A Western Digital Company<o:p></o:p></span></p>
<p class="MsoNormal"><a href="mailto:derek.stewart@hgst.com"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#0563C1">derek.stewart@hgst.com</span></a><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#1F497D"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#1F497D">Office: (408) 717-5901<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><img border="0" width="288" height="57" id="Picture_x0020_1" src="cid:image001.gif@01D0CC6F.51841070" alt="HGST_aWDco_closing_sm_wLLD"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:8.0pt;font-family:"Arial",sans-serif;color:#1F497D">3403 Yerba Buena Rd<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:8.0pt;font-family:"Arial",sans-serif;color:#1F497D">San Jose, CA 95135<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> pw_forum-bounces@pwscf.org [mailto:pw_forum-bounces@pwscf.org]
<b>On Behalf Of </b>Umesh Roy<br>
<b>Sent:</b> Saturday, August 1, 2015 4:22 AM<br>
<b>To:</b> pw_forum@pwscf.org<br>
<b>Subject:</b> [Pw_forum] Separation between acoustic modes and optical modes<o:p></o:p></span></p>
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<p class="MsoNormal">Dear All,<o:p></o:p></p>
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<p class="MsoNormal"> I have calculated modes of vibration of Iron in different directions for a fix phonon wave vector q (in a large number of directions). Since in Quantum espresso phonon modes are printed in increasing order for a given q vector.
For a small group of q the acoustic and optical branches do not overlap so, we can easily separate out the acoustic branch from the optical branch. As we increase the magnitude of q the acoustic branch and the optical branch get mixed up. So , how to separate
out the acoustic modes or is there any way of filtering the optical modes?<o:p></o:p></p>
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<p class="MsoNormal">Thank you in advance<o:p></o:p></p>
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<p class="MsoNormal"><b><i><span style="color:blue;background:#F3F3F3">Umesh Chandra Roy</span></i></b><i><span style="color:blue;background:#F3F3F3"><br>
Research Scholar, School of Physical Sciences<br>
Jawaharlal Nehru University, New Delhi-110067,</span></i><o:p></o:p></p>
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<p class="MsoNormal"><i><span style="color:blue;background:#F3F3F3">India.</span></i><o:p></o:p></p>
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<p class="MsoNormal"><a href="mailto:Email%3Aumesh24crp@gmail.com" target="_blank"><i><span style="font-size:10.0pt;background:#F3F3F3">Email:</span><b><span style="background:#F3F3F3">umesh24crp@gmail.com</span></b></i></a><o:p></o:p></p>
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<p class="MsoNormal"><i><span style="color:blue;background:#F3F3F3">Mobile:<b>+919868022722</b></span></i><o:p></o:p></p>
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