<div dir="ltr">Hi
Mohaddeseh,<div><br></div><div>One thing I want to add regarding your 1st question. You are getting I+R modes because your system may not have inversion symmetry (you can check in scf.out).</div><div><br></div><div>Best,</div><div>Hari Paudyal</div><div><br></div><div> <br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Aug 12, 2020 at 10:45 AM Mona Asadinamin <<a href="mailto:Mona.a@uga.edu">Mona.a@uga.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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Dear Mohaddeseh:</div>
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You are right, it means IR and Raman active simultaneously. </div>
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Regarding the scf threshold, increasing it results in more accuracy and normally it should be very tight, something like 1.d-15 or even less. It definitely does not turn frequencies from positive to negative. It helps to bring the system out of unstable point
in the potential energy surface that causes negative frequencies. </div>
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<font face="Times New Roman, Times, serif" size="3">Best regards; </font></p>
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<span style="font-family:"Times New Roman",Times,serif">Mona Asadi Namin</span></p>
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<span style="color:rgb(0,0,0);font-family:"Times New Roman",Times,serif">E</span><span style="font-family:"Times New Roman",Times,serif">mail:</span><span style="font-family:"Times New Roman",Times,serif;color:rgb(149,79,114)"><a href="mailto:mona.a@uga.edu" style="font-family:"Times New Roman",serif;color:rgb(149,79,114)" target="_blank">mona.a@uga.ed</a>u<a href="mailto:mona.a@uga.edu" target="_blank"></a></span><span style="font-family:"Times New Roman",Times,serif"> </span></p>
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<span style="font-family:"Times New Roman",Times,serif">P</span><span style="font-family:"Times New Roman",Times,serif">hone: +1-215-906-23-92</span><span style="font-family:"Times New Roman",Times,serif"> </span><span style="font-family:"Times New Roman",Times,serif">
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<div id="gmail-m_2619678107936060770divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> users <<a href="mailto:users-bounces@lists.quantum-espresso.org" target="_blank">users-bounces@lists.quantum-espresso.org</a>> on behalf of Mohad Abbasnejad <<a href="mailto:mohaddeseh.abbasnejad@gmail.com" target="_blank">mohaddeseh.abbasnejad@gmail.com</a>><br>
<b>Sent:</b> Wednesday, August 12, 2020 8:16 AM<br>
<b>To:</b> <a href="mailto:users@lists.quantum-espresso.org" target="_blank">users@lists.quantum-espresso.org</a> <<a href="mailto:users@lists.quantum-espresso.org" target="_blank">users@lists.quantum-espresso.org</a>><br>
<b>Subject:</b> [QE-users] Regarding phonon calculations</font>
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<div><font color="BA0C2F">[EXTERNAL SENDER - PROCEED CAUTIOUSLY]</font><br>
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<div>Dear QE users,</div>
<div><br>
</div>
<div>
<div>Hello </div>
I hope everybody is well.<br>
I have two questions regarding phonon calculations.</div>
<div>1- I have calculated the frequency for special q point in my structure shown as follow:</div>
<div><br>
</div>
<div><font color="#ff0000"> Mode symmetry, C_3v (3m) point group:<br>
<br>
freq ( 1 - 2) = -59.6 [cm-1] --> E L_3 I+R<br>
freq ( 3 - 3) = -48.4 [cm-1] --> A_1 L_1 I+R<br>
freq ( 4 - 5) = 162.4 [cm-1] --> E L_3 I+R<br>
freq ( 6 - 6) = 227.4 [cm-1] --> A_1 L_1 I+R<br>
freq ( 7 - 7) = 250.8 [cm-1] --> A_2 L_2<br>
freq ( 8 - 8) = 295.5 [cm-1] --> A_2 L_2<br>
freq ( 9 - 10) = 299.4 [cm-1] --> E L_3 I+R<br>
freq ( 11 - 12) = 308.1 [cm-1] --> E L_3 I+R<br>
freq ( 13 - 14) = 382.0 [cm-1] --> E L_3 I+R<br>
freq ( 15 - 16) = 435.0 [cm-1] --> E L_3 I+R<br>
freq ( 17 - 17) = 456.0 [cm-1] --> A_1 L_1 I+R<br>
freq ( 18 - 18) = 513.6 [cm-1] --> A_2 L_2<br>
freq ( 19 - 20) = 521.9 [cm-1] --> E L_3 I+R<br>
freq ( 21 - 21) = 571.4 [cm-1] --> A_1 L_1 I+R<br>
freq ( 22 - 23) = 578.0 [cm-1] --> E L_3 I+R<br>
freq ( 24 - 24) = 614.8 [cm-1] --> A_1 L_1 I+R<br>
freq ( 25 - 25) = 620.5 [cm-1] --> A_2 L_2<br>
freq ( 26 - 27) = 635.4 [cm-1] --> E L_3 I+R<br>
freq ( 28 - 29) = 651.0 [cm-1] --> E L_3 I+R<br>
freq ( 30 - 30) = 653.0 [cm-1] --> A_2 L_2</font><br>
<br>
I am wondering if somebody can tell me the meaning of I+R modes.<br>
Does it mean Raman and infrared are active simultaneously for this mode?</div>
<div><br>
</div>
<div>2- I am wondering if increasing the<font face="arial, sans-serif"> <span style="color:rgb(0,0,0)">threshold for self-consistency may influence the frequencies significantly such that it causes the frequency value from positive to negative. Is the </span></font>default
of the program reasonable?</div>
<div><br>
</div>
<div>Any help would be appreciated.<br>
<br>
Bests<br>
Mohaddeseh<br>
</div>
-- <br>
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Mohaddeseh Abbasnejad, <br>
Assistant Professor of Physics,<br>
Faculty of Physics, <br>
Shahid Bahonar University of Kerman,<br>
Kerman, Iran<br>
P.O. Box 76169-133<br>
Tel: +98 34 31322199<br>
Fax: +98 34 33257434<br>
Cellphone: +98 917 731 7514<br>
E-Mail: <a href="mailto:mohaddeseh.abbasnejad@gmail.com" target="_blank">mohaddeseh.abbasnejad@gmail.com</a><br>
Website: <a href="http://academicstaff.uk.ac.ir/moabbasnejad" target="_blank">academicstaff.uk.ac.ir/moabbasnejad</a>
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