<div dir="ltr">It is because you did not finish all the steps to analyse the data.<div><br></div><div>I got a similar problem before and I remember it is possible to obtain a file that has as the vectors of the modes that can be viewed in the xcrysden. Unfortunately I don't run simulations phonon simulations anymore, I couldn't remember everything I did in the past. <br>
</div><div><br></div><div><div>I am pasting a manual section that explains it in details. (I also change the color to red the point I think might solve your issue.)</div><div><br></div><div><br></div><div><h2 style="color:rgb(0,0,0);font-family:'Times New Roman'">
<a name="SECTION00052000000000000000">4.2 Calculation of interatomic force constants in real space</a></h2><p style="color:rgb(0,0,0);font-family:'Times New Roman';font-size:medium">First, dynamical matrices are calculated and saved for a suitable uniform grid of <b>q</b>-vectors (only those in the Irreducible Brillouin Zone of the crystal are needed). Although this can be done one <b>q</b>-vector at the time, a simpler procedure is to specify variable <tt>ldisp=.true.</tt> and to set variables <tt>nq1</tt>, <tt>nq2</tt>,<tt>nq3</tt> to some suitable Monkhorst-Pack grid, that will be automatically generated, centered at <img width="16" height="35" align="MIDDLE" border="0" src="http://www.quantum-espresso.org/wp-content/uploads/Doc/ph_user_guide/img1.png" alt="$ \bf q$"> = 0 .</p>
<p style="color:rgb(0,0,0);font-family:'Times New Roman';font-size:medium">Second, code <tt>q2r.x</tt> reads the dynamical matrices produced in the preceding step and Fourier-transform them, writing a file of Interatomic Force Constants in real space, up to a distance that depends on the size of the grid of <b>q</b>-vectors. Input documentation in the header of <tt>PHonon/PH/q2r.f90</tt>.</p>
<p style="font-family:'Times New Roman';font-size:medium"><font color="#ff0000"><u>Program <tt>matdyn.x</tt> may be used to produce phonon modes and frequencies at any <b>q</b> using the Interatomic Force Constants file as input. Input documentation in the header of <tt>PHonon/PH/matdyn.f90</tt>.</u><br>
</font></p><p style="color:rgb(0,0,0);font-family:'Times New Roman';font-size:medium">See Example 02 for a complete calculation of phonon dispersions in AlAs. </p><p style="color:rgb(0,0,0);font-family:'Times New Roman';font-size:medium">
source: <a href="http://www.quantum-espresso.org/wp-content/uploads/Doc/ph_user_guide/node1.html">http://www.quantum-espresso.org/wp-content/uploads/Doc/ph_user_guide/node1.html</a><br></p><p style="color:rgb(0,0,0);font-family:'Times New Roman';font-size:medium">
<br></p><p style="color:rgb(0,0,0);font-family:'Times New Roman';font-size:medium">I hope it will solve your issue.</p><p style="color:rgb(0,0,0);font-family:'Times New Roman';font-size:medium"><br></p><p style="color:rgb(0,0,0);font-family:'Times New Roman';font-size:medium">
Best regards,</p><p style="color:rgb(0,0,0);font-family:'Times New Roman';font-size:medium"><br></p><p style="color:rgb(0,0,0);font-family:'Times New Roman';font-size:medium">Filipe</p></div></div><div class="gmail_extra">
<br><br><div class="gmail_quote">On Tue, Apr 1, 2014 at 8:49 AM, Peram sreenivasa reddy <span dir="ltr"><<a href="mailto:peramsreenivas@gmail.com" target="_blank">peramsreenivas@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr"><div><div><div><div>Dear xirainbow,<br><br></div>Thank you very much for your replay.<br><br></div>In that case.dyn1 file also it is giving same only as in the case.ph.out file.<br><br></div>Please give me more clarification.<br>
<br></div>Thanking you.<div><div class="h5"><br><div class="gmail_extra"><br><br><div class="gmail_quote">On Tue, Apr 1, 2014 at 3:15 PM, xirainbow <span dir="ltr"><<a href="mailto:nkxirainbow@gmail.com" target="_blank">nkxirainbow@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">You can find the answer at the end of *.dyn* files.<br>
<div><div><br>
On Mon, Mar 31, 2014 at 11:10 PM, Peram sreenivasa reddy<br>
<<a href="mailto:peramsreenivas@gmail.com" target="_blank">peramsreenivas@gmail.com</a>> wrote:<br>
> Dear Pwscf,<br>
><br>
> In my phonon calculations i got one imaginary mode in gamma to X direction.<br>
> I want to know which mode it is? and due to which atom it is happening?<br>
><br>
> I checked the case.ph.out file. In this file it is given like below.<br>
><br>
> Mode symmetry, O_h (m-3m) point group:<br>
> omega( 1 - 3) = -16.6 [cm-1] --> T_1u G_15 G_4- I<br>
> omega( 4 - 6) = 122.3 [cm-1] --> T_1u G_15 G_4- I<br>
> omega( 7 - 9) = 145.0 [cm-1] --> T_2g G_25' G_5+ R<br>
> omega( 10 - 12) = 258.5 [cm-1] --> T_1u G_15 G_4- I<br>
><br>
> Here i am attaching the case.agr file<br>
><br>
> Here all acoustic modes are given with same frequency. How can know that<br>
> particular mode name.<br>
><br>
><br>
> My system is X2YZ type. How can i know this imaginary mode is due to which<br>
> atom. I plotted partial phonon density of states also. But all atoms are<br>
> giving same contribution in this acoustic mode region.<br>
><br>
> Thank you in advance.<br>
><br>
><br>
><br>
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Hui Wang<br>
School of physics, Henan University of Science and Technology, Henan, China<br>
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