<div dir="ltr">Thanks Paolo. When I introduced small smearing( about 0.02eV) the issue is resolved. The smearing is significantly smaller than the bandgap. So is introducing smearing for semiconductors correct? </div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, Jan 17, 2020 at 12:32 PM Paolo Giannozzi <<a href="mailto:p.giannozzi@gmail.com">p.giannozzi@gmail.com</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"><div dir="ltr"><div>"Negative" actually means "imaginary". If "negative" frequencies appear in the three zero-frequency acoustic phonons at Gamma, and if they are small (no more than a few tens of cm-1), there is nothing to worry about:</div><div><a href="http://www.quantum-espresso.org/resources/faq/phonons#7.2" target="_blank">http://www.quantum-espresso.org/resources/faq/phonons#7.2</a></div><div><br></div><div>Paolo<br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Thu, Jan 16, 2020 at 8:57 PM Sheikh Ziauddin Ahmed <<a href="mailto:sza9wz@virginia.edu" target="_blank">sza9wz@virginia.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"><div dir="ltr">Hello <div><br></div><div>I am trying to compute the phonon frequencies ofI nAs. I am getting negative frequencies near the gamma point. I also tried with epsil =.true. But that does not change it. Here is the SCF and PH input I am using. </div><div><br></div><div>Please give me some suggestions on what I can do to fix this problem.</div><div><br></div><div>SCF:</div><div> &control<br> calculation='scf'<br> restart_mode='from_scratch',<br> prefix='test_i',<br> pseudo_dir = '/InAs_phonon',<br> outdir='./temp'<br> tstress = .true. ,<br> tprnfor = .true. ,<br> /<br> &system<br> ibrav=2, celldm(1) =11.4485, nat=2, ntyp=2,<br> ecutwfc = 50, ecutrho = 250<br> /<br> &electrons<br> conv_thr = 1.0e-9<br> mixing_beta = 0.7<br> mixing_mode = 'local-TF'<br> /<br>ATOMIC_SPECIES<br> In 114.818 In.pz-dn-kjpaw_psl.0.2.2.UPF<br> As 74.92 As.pz-n-kjpaw_psl.0.2.UPF<br>ATOMIC_POSITIONS {crystal}<br> In 0.0 0.0 0.0<br> As 0.25 0.25 0.25<br>K_POINTS automatic<br>6 6 6 0 0 0<br><div><br></div><div><br></div><div>PH: </div><div> &inputph<br> tr2_ph=1d-14<br> prefix='test_i',<br> ldisp=.true.<br> !epsil=.true.<br> nq1=3, nq2=3, nq3=3<br> amass(1)=114.818<br> amass(2)=74.92<br> outdir='/scratch/sza9wz/'<br> fildyn = 'test_i-3.dyn'<br> /<br></div><div><br></div><div>Regards,</div><div>Sheikh Ahmed<br>University of Virginia</div>-- <br><div dir="ltr"><div dir="ltr"><div style="margin-bottom:0px;margin-left:0px;padding-bottom:5px"><div><div dir="ltr"><span><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div style="font-size:12.8px"><font color="#444444"><b>Sheikh Ziauddin Ahmed </b></font></div><div style="font-size:12.8px"><font color="#444444">PhD Candidate</font></div><div style="font-size:12.8px"><font color="#444444">Charles L. Brown Department of Electrical and Computer Engineering</font></div><div style="font-size:12.8px"><font color="#444444">University of Virginia</font></div><div style="font-size:12.8px"><font color="#444444">Email<font color="#888888">:</font><a href="mailto:sza9wz@virginia.edu" target="_blank">sza9wz<u>@virginia.edu</u></a></font></div><div><div style="font-size:12.8px"><font color="#444444">LinkedIn</font><font color="#000000">: </font><span style="color:rgb(136,136,136);font-size:12.8px"><a href="https://www.linkedin.com/in/sheikh-ziauddin-ahmed" target="_blank">https://www.linkedin.com/in/sheikh-ziauddin-ahmed</a></span></div></div></div></div></div></div></div></span></div><div style="font-size:12.8px"></div></div></div><div style="font-size:12.8px"></div></div></div></div></div>
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Quantum ESPRESSO is supported by MaX (<a href="http://www.max-centre.eu/quantum-espresso" rel="noreferrer" target="_blank">www.max-centre.eu/quantum-espresso</a>)<br>
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<a href="https://lists.quantum-espresso.org/mailman/listinfo/users" rel="noreferrer" target="_blank">https://lists.quantum-espresso.org/mailman/listinfo/users</a></blockquote></div><br clear="all"><div><br></div>-- <br><div dir="ltr" class="gmail_signature"><div dir="ltr"><div style="margin-bottom:0px;margin-left:0px;padding-bottom:5px"><div><div dir="ltr"><span><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div style="font-size:12.8px"><font color="#444444"><b>Sheikh Ziauddin Ahmed </b></font></div><div style="font-size:12.8px"><font color="#444444">PhD Candidate</font></div><div style="font-size:12.8px"><font color="#444444">Charles L. Brown Department of Electrical and Computer Engineering</font></div><div style="font-size:12.8px"><font color="#444444">University of Virginia</font></div><div style="font-size:12.8px"><font color="#444444">Email<font color="#888888">:</font><a href="mailto:sza9wz@virginia.edu" target="_blank">sza9wz<u>@virginia.edu</u></a></font></div><div><div style="font-size:12.8px"><font color="#444444">LinkedIn</font><font color="#000000">: </font><span style="color:rgb(136,136,136);font-size:12.8px"><a href="https://www.linkedin.com/in/sheikh-ziauddin-ahmed" target="_blank">https://www.linkedin.com/in/sheikh-ziauddin-ahmed</a></span></div></div></div></div></div></div></div></span></div><div style="font-size:12.8px"></div></div></div><div style="font-size:12.8px"></div></div></div>