<div dir="ltr"><div><div><div><div>I have a structure that I supposed was well relaxed; Total force = 0.000624 and P= -0.00. <br></div>But I still get negative frequencies.<br><br></div>Isn't such Forec/pressure good enough?<br><br></div>Comments shall be appreciated.<br><br></div>Isaiah<br></div><div class="gmail_extra"><br><div class="gmail_quote">On Sat, Jul 22, 2017 at 11:24 AM, Arles V. Gil Rebaza <span dir="ltr"><<a href="mailto:arvifis@gmail.com" target="_blank">arvifis@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Dear Mohammad, try to relax your system using "relax" or "vc-relax" in order to reduce the interatomic forces. After that use "scf" calculation<div><br></div><div>Furthermore, &cell and &ions parts and forc_conv_thr tag does not work for scf calculations. Please read the QE manual.</div><div><br></div><div>Best</div><div><br></div><div>Dr. Arles V. Gil Rebaza</div><div>IFLP - Argentina<div><div class="h5"><br><br>El sábado, 22 de julio de 2017, Mohammad Alidoosti <<a href="mailto:m.alidoosti@gmail.com" target="_blank">m.alidoosti@gmail.com</a>> escribió:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><br clear="all"><div>Dear PWSCF users,</div><div><br></div><div>I am doing phonon frequencies calculations for Graphene-oxide. In proximity to the Gamma point, I get small negative frequencies. As far as I know this is a known problem, I have tried to increase "forc_conv_thr" and "tr2_ph" to 1.0d-6 and 1.0d-16, respectively, but it doesn't work. Is there any suggestion for solving this problem?</div><div>Hear is the scf input file : </div><div>******************************<wbr>******************************<wbr>*********</div><div><div> &control</div><div> title = GO</div><div> calculation = 'scf'<span style="white-space:pre-wrap"> </span></div><div> restart_mode = 'from_scratch'<span style="white-space:pre-wrap"> </span></div><div> prefix = 'GO-ph'</div><div> pseudo_dir = '/home/pseudo'</div><div> outdir = './tmp/'<span style="white-space:pre-wrap"> </span></div><div> nstep = 200 , </div><div> tstress = .true. ,</div><div> tprnfor = .true. ,</div><div> verbosity='high',</div><div> forc_conv_thr= 1.0d-6</div><div> /</div><div> &system</div><div> ibrav = 0<span style="white-space:pre-wrap"> </span> </div><div> nat = 12<span style="white-space:pre-wrap"> </span></div><div> ntyp = 3<span style="white-space:pre-wrap"> </span></div><div> ecutwfc = 80<span style="white-space:pre-wrap"> </span></div><div> ecutrho = 400</div><div> occupations = 'smearing'<span style="white-space:pre-wrap"> </span></div><div> smearing='methfessel-paxton', </div><div> degauss = 0.001</div><div>/</div><div> &electrons</div><div>conv_thr= 1.0d-8</div><div>mixing_beta = 0.7</div><div> electron_maxstep = 200,<span style="white-space:pre-wrap"> </span></div><div> /</div><div> &IONS</div><div>/</div><div>&CELL</div><div>cell_dofree = '2Dxy',</div><div>/</div><div>ATOMIC_SPECIES</div><div> C 12.0107 C.pbe-n-kjpaw_psl.0.1.UPF</div><div> O 15.999 O.pbe-n-kjpaw_psl.0.1.UPF</div><div> H 1.008 H.pbe-kjpaw_psl.0.1.UPF</div><div>CELL_PARAMETERS (angstrom)</div><div> 4.990235060 0.054948389 0.000000000</div><div> -2.541880421 4.219875071 0.000000000</div><div> 0.000000000 0.000000000 25.000000000</div><div><br></div><div>ATOMIC_POSITIONS (angstrom)</div><div>O -0.021826634 0.250928937 1.721705471</div><div>H 0.809321037 0.681392784 1.997855886</div><div>O -0.031523808 1.135550155 -1.892027240</div><div>H 0.808877574 0.723408478 -2.168118129</div><div>C 0.047350145 0.017290716 0.288486347</div><div>C 0.032454255 1.370630042 -0.458840404</div><div>C -1.237500438 2.119007372 -0.142173618</div><div>C -1.224236423 3.485316018 -0.033121650</div><div>C 1.242549808 3.515955831 -0.028144886</div><div>C 1.285890831 2.150271662 -0.137183942</div><div>C 2.528922921 1.430926894 -0.090219298</div><div>C 2.544546281 0.011979550 -0.080086702</div><div>K_POINTS automatic<span style="white-space:pre-wrap"> </span> </div><div>15 15 1 0 0 0</div></div><div>******************************<wbr>******************************<wbr>*******</div><div><br></div><div>Thanks in advance.</div><div><br></div><div>Mohammad Alidoosti</div>-- <br><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div style="margin-bottom:0px;margin-left:0px;padding-bottom:5px"><div><div dir="ltr"><div><div dir="ltr"><font><span style="font-family:arial,helvetica,sans-serif"><font style="font-size:12.8px" color="#888888">Institute for Research in Fundamental Sciences (IPM)</font><br><font style="font-size:12.8px" color="#888888">School of Nano-Science</font><br><font style="font-size:12.8px" color="#888888">Shahid Farbin Alley</font><br><font style="font-size:12.8px" color="#888888">Shahid Lavasani st</font></span></font></div><div dir="ltr"><font><span style="font-family:arial,helvetica,sans-serif"><font color="#888888">P.Code: 19538-33511</font></span></font></div><div dir="ltr"><font><span style="font-size:12.8px;color:rgb(136,136,136);font-family:arial,helvetica,sans-serif">Tehran, Iran</span><span style="font-family:arial,helvetica,sans-serif"><font color="#888888"><br></font></span></font></div><div dir="ltr"><font><span style="font-family:arial,helvetica,sans-serif"><font style="font-size:12.8px" color="#888888">Tel: </font><font size="2" color="#999999">+98 21 2310 -3070</font><br></span></font></div><div style="font-size:12.8px;color:rgb(136,136,136)"><font color="#888888"><span style="font-family:arial,helvetica,sans-serif"><br></span></font></div></div></div><div style="font-size:12.8px"></div></div></div><div style="font-size:12.8px"></div></div></div></div></div></div></div></div></div></div></div></div></div>
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</blockquote></div></div></div><span class="HOEnZb"><font color="#888888"><br><br>-- <br>###---------> Arles V. <---------###<br>
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