<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Wed, Apr 27, 2016 at 11:04 AM, Yuma Nakamura <span dir="ltr"><<a href="mailto:zcym15@mails.tsinghua.edu.cn" target="_blank">zcym15@mails.tsinghua.edu.cn</a>></span> wrote:<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="line-height:16.8px"><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"><br></div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"><br></div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">With the reported set of thresholds(etot_conv_thr, forc_conv_thr, conv_thr and tr2_ph), negative frequency appears at Gamma point.</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">It seems that this negative frequency is not small enough to be modified by acoustic sum rule. (please check the output below)</div></div></blockquote><div><br></div><div>-18 cm^-1 without Acoustic Sum Rule? it seems to me in an acceptable range of values, not that big.<br><br></div><div>You may want to verify if your results change appreciably if you choose a wave-vector grid that is commensurate with the k-point grid (for instance: 20 20 1 for k-points, 5 5 1 for phonon wavevectors). In some metallic systems, characterized by the presence of semicore states, it was observed that calculations with "commensurate" grids yield much better results than with "uncommensurate" ones, for unclear reasons<br><br></div><div>Paolo<br></div><div><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="line-height:16.8px"><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">I understand this is because its structure is not stable.</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">In the final relaxed state, the stress is -0.02 kbar in xx(yy) component and -0.24 kbar in zz component. </div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"><br></div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">Is it optimization problem or do I miss some important control tags?</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"><br></div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"><br></div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">I used in Quantum Espresso 5.2.1</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"><br></div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">Here is my trial set of thresholds and result.</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"><br></div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"><br></div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">————————————————optimization & scf————————————</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">calculation mode = vc-relax </div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">ion_dynamics = bfgs </div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">ecutwfc = 65 *</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">etot_conv_thr =1.0D-12 * </div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">forc_conv_thr =1.0D-6 * </div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">conv_thr =1.0D-14 </div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">k-point<span style="white-space:pre-wrap"> </span> =21x21x1 *</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">————————————————ph run———————————————————————— </div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">tr2_ph =1.0D-16</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">q-point =5x5x1 *</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">——————————————————————————————————————————————</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"><br></div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">* theses values are referred from the literature, the other values are not mentioned and determined by myself.</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"><br></div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"><br></div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"><br></div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> Diagonalizing the dynamical matrix</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"><br></div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> q = ( 0.000000000 0.000000000 0.000000000 )</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"><br></div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> **************************************************************************</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> freq ( 1) = -0.551779 [THz] = -18.405359 [cm-1]</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> freq ( 2) = -0.551779 [THz] = -18.405359 [cm-1]</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> freq ( 3) = 0.352400 [THz] = 11.754783 [cm-1]</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> freq ( 4) = 3.460541 [THz] = 115.431227 [cm-1]</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> freq ( 5) = 5.407571 [THz] = 180.377167 [cm-1]</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> freq ( 6) = 5.407571 [THz] = 180.377167 [cm-1]</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> **************************************************************************</div><div><div><font face="MS PGothic, sans-serif" size="3"><span style="line-height:normal"> Mode symmetry, C_3v (3m) point group:</span></font></div><div><font face="MS PGothic, sans-serif" size="3"><span style="line-height:normal"><br></span></font></div><div><font face="MS PGothic, sans-serif" size="3"><span style="line-height:normal"> freq ( 1 - 2) = -18.4 [cm-1] --> E L_3 I+R</span></font></div><div><font face="MS PGothic, sans-serif" size="3"><span style="line-height:normal"> freq ( 3 - 3) = 11.8 [cm-1] --> A_1 L_1 I+R</span></font></div><div><font face="MS PGothic, sans-serif" size="3"><span style="line-height:normal"> freq ( 4 - 4) = 115.4 [cm-1] --> A_1 L_1 I+R</span></font></div><div><font face="MS PGothic, sans-serif" size="3"><span style="line-height:normal"> freq ( 5 - 6) = 180.4 [cm-1] --> E L_3 I+R</span></font></div><div><font face="MS PGothic, sans-serif" size="3"><span style="line-height:normal"><br></span></font></div><div><font face="MS PGothic, sans-serif" size="3"><span style="line-height:normal"><br></span></font></div></div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">In those setups, I got converged results(even phonon frequency is negative).</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"><br></div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"><br></div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">The complete input files are following. The output files are attached.</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"><br></div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"><br></div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"><br></div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">—————————————————————pw.x———————————————————————————— </div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> &control</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> calculation = 'vc-relax' </div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> restart_mode = 'from_scratch' </div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> outdir = './'</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> prefix = 'stanene' </div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> tstress = .true. </div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> tprnfor = .true. </div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> pseudo_dir = './'</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> verbosity = 'high'</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> etot_conv_thr = 1.0E-12</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> forc_conv_thr = 1.0D-6</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"><br></div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> /</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> &system</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> ibrav = 0</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> celldm(1) = 8.83069022</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> nat = 2</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> ntyp = 1</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> ecutwfc = 65</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> ecutrho = 600</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> degauss = 0.02</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> smearing ='mp'</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> occupations ='smearing',</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"><br></div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"><br></div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"><br></div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">/</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> &electrons</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> diagonalization = 'david'</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> mixing_mode = 'plain'</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> mixing_beta = 0.7</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> conv_thr = 1.0d-14</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> /</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> &ions</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> ion_dynamics = 'bfgs'</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> /</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> &cell</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> cell_dofree = '2Dxy'</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> /</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">ATOMIC_SPECIES</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">Sn 118.710 Sn.pbe-dn-rrkjus_psl.0.2.UPF</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">CELL_PARAMETERS (alat= 8.83069022)</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> 1.002153232 0.000000000 0.000000000</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> -0.501076616 0.867890158 0.000000000</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> 0.000000000 0.000000000 4.061049000</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">ATOMIC_POSITIONS {crystal}</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">Sn 0.666666666 0.333333333 -0.000019757</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">Sn 0.333333333 0.666666667 0.044809919</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">K_POINTS automatic</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">36 36 1 0 0 0</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">—————————————————————ph.x————————————————————————————</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">phonons of Sn</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> &inputph</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> tr2_ph=1.0d-16,</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> prefix='stanene',</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> ldisp=.true.,</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> nq1=5, nq2=5, nq3=1</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> start_q=1 </div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> last_q=1 </div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> amass(1)=118.710,</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> outdir=“.//1”,</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> fildyn='stanene.dyn',</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"> /</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"><br></div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"><br></div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"><br></div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal"><br></div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">Best regards,</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">+++++++++++++++++</div><span class="HOEnZb"><font color="#888888"><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">Yuma Nakamura</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">Double Master Degree candidate </div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">Dept of Chemistry in Tsinghua University, China</div><div style="font-family:'MS PGothic',sans-serif;font-size:medium;line-height:normal">Dept of Physics in Tohoku University, Japan</div><div style="font-family:'MS PGothic',sans-serif;font-size:12pt;line-height:normal"><br></div></font></span></div><div style="font-family:'MS PGothic',sans-serif;font-size:12pt;line-height:normal"><br></div><div style="font-family:'MS PGothic',sans-serif;font-size:12pt;line-height:normal"><br></div><br><br><br><br>_______________________________________________<br>
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<a href="http://pwscf.org/mailman/listinfo/pw_forum" rel="noreferrer" target="_blank">http://pwscf.org/mailman/listinfo/pw_forum</a><br></blockquote></div><br><br clear="all"><br>-- <br><div class="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div>Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,<br>Univ. Udine, via delle Scienze 208, 33100 Udine, Italy<br>Phone +39-0432-558216, fax +39-0432-558222<br><br></div></div></div></div></div>
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