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    <p>Dear Jibiao,</p>
    <p>One explanation could be that the thresholds you chose are not
      tight enough.<br>
      You could check whether the problem is alleviated if you tighten
      these.<br>
      For the scf calculation, set conv_thr in electrons to something
      much tighter than the default, I would suggest 1.0D-10.<br>
      Also your threshold for tr2_ph in inputph can be tighter. If the
      discrepancy decreases, than the frequencies are just imprecise due
      to bad convergence.<br>
    </p>
    <p>Best,</p>
    <p>    Leonid Kahle</p>
    <p><br>
    </p>
    <div class="moz-cite-prefix">On 10/9/19 3:48 PM, Jibiao Li wrote:<br>
    </div>
    <blockquote type="cite"
      cite="mid:tencent_4DA3CE452A34C76B33685A1BFA3DEF7F0F07@qq.com">
      <meta http-equiv="Content-Type" content="text/html;
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      <div>Dear Prof. Paolo Giannozzi,</div>
      <div><br>
      </div>
      <div>The two computers have the exact same OS (ubuntu), compilers
        (ifort), libraries, and parallel environments installed. It
        really strange why different results produced by the same
        inputs. Can anyone help me?</div>
      <div><br>
      </div>
      <div>Best<br>
      </div>
      <div><br>
      </div>
      <div>
        <div style="color:#909090;font-family:Arial
          Narrow;font-size:12px">------------------</div>
        <div style="font-size:14px;font-family:Verdana;color:#000;">
          <div><i><font size="2" face="Times New Roman" color="#0000ff"><b>Dr.
                  Jibiao Li, </b></font></i></div>
          <div><i><font size="2" face="Times New Roman" color="#0000ff"><b>Department
                  of Material Science and Engineering</b></font></i></div>
          <div><i><font size="2" face="Times New Roman" color="#0000ff"><b>Yangtze
                  Normal University</b></font></i></div>
          <div><i><font face="Times New Roman"><font size="2"><font
                    color="#0000ff"><b><span style="text-align: left;
                        text-transform: none; line-height: 21px;
                        text-indent: 0px; letter-spacing: normal;
                        font-variant: normal; text-decoration: none;
                        word-spacing: 0px; display: inline !important;
                        white-space: normal; orphans: 2; float: none;
                        -webkit-text-stroke-width: 0px;
                        background-color: transparent;">Juxian Dadao
                        16#,</span> Fuling, Chongqing, China</b></font></font></font></i></div>
          <div><i><font size="2" face="Times New Roman" color="#0000ff"><b>Email:
                  <a class="moz-txt-link-abbreviated" href="mailto:jibiaoli@yznu.edu.cn">jibiaoli@yznu.edu.cn</a>, <a class="moz-txt-link-abbreviated" href="mailto:jibiaoli@foxmail.com">jibiaoli@foxmail.com</a>,
                  <a class="moz-txt-link-abbreviated" href="mailto:jibiao.li@hotmail.com">jibiao.li@hotmail.com</a></b></font></i></div>
          <div><i><font size="2" face="Times New Roman" color="#0000ff"><b>Homepage:
                  <a class="moz-txt-link-freetext" href="https://www.researchgate.net/profile/Jibiao_Li">https://www.researchgate.net/profile/Jibiao_Li</a></b></font></i></div>
        </div>
      </div>
      <div> </div>
      <div>
        <div><br>
        </div>
        <div><br>
        </div>
        <div style="font-size: 12px;font-family: Arial
          Narrow;padding:2px 0 2px 0;">------------------ Original ------------------</div>
        <div style="font-size: 12px;background:#efefef;padding:8px;">
          <div><b>From:</b> "p.giannozzi"<a class="moz-txt-link-rfc2396E" href="mailto:p.giannozzi@gmail.com"><p.giannozzi@gmail.com></a>;</div>
          <div><b>Date:</b> Wed, Oct 9, 2019 09:42 PM</div>
          <div><b>To:</b> "Quantum ESPRESSO users
            Forum"<a class="moz-txt-link-rfc2396E" href="mailto:users@lists.quantum-espresso.org"><users@lists.quantum-espresso.org></a>;<wbr></div>
          <div><b>Subject:</b> Re: [QE-users] Computer dependent phonon
            frequencies</div>
        </div>
        <div><br>
        </div>
        <div dir="ltr">
          <div>Hard to say with no knowledge (or even with the
            knowledge) of which computers, compilers, libraries,
            parallel execution, ... produce strange results.<br>
          </div>
          <div><br>
          </div>
          <div>Paolo</div>
        </div>
        <br>
        <div class="gmail_quote">
          <div class="gmail_attr" dir="ltr">On Wed, Oct 9, 2019 at 2:19
            PM Jibiao Li <<a href="mailto:jibiaoli@foxmail.com"
              moz-do-not-send="true">jibiaoli@foxmail.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>Dear QE experts,</div>
            <div><br>
            </div>
            <div>I am studying mixed H2O/OH phase on Ag(111) using QE
              6.4.1. To my suprise, however, to different computers gave
              totally different vibrational frequencies, with the exact
              same input files. Is there anybody to help me?</div>
            <div><br>
            </div>
            <div>Computer A gave</div>
            <div>     freq ( 46 - 46) =         24.2  [cm-1]   -->
              A               I+R<br>
                   freq ( 47 - 47) =         72.8  [cm-1]   -->
              A               I+R<br>
                   freq ( 48 - 48) =        137.6  [cm-1]   -->
              A               I+R<br>
                   freq ( 49 - 49) =        199.5  [cm-1]   -->
              A               I+R<br>
                   freq ( 50 - 50) =        308.7  [cm-1]   -->
              A               I+R<br>
                   freq ( 51 - 51) =        379.5  [cm-1]   -->
              A               I+R<br>
                   freq ( 52 - 52) =        585.2  [cm-1]   -->
              A               I+R<br>
                   freq ( 53 - 53) =        800.0  [cm-1]   -->
              A               I+R<br>
                   freq ( 54 - 54) =        872.2  [cm-1]   -->
              A               I+R<br>
                   freq ( 55 - 55) =        901.9  [cm-1]   -->
              A               I+R<br>
                   freq ( 56 - 56) =        998.4  [cm-1]   -->
              A               I+R<br>
                   freq ( 57 - 57) =       1529.7  [cm-1]   -->
              A               I+R<br>
                   freq ( 58 - 58) =       2914.9  [cm-1]   -->
              A               I+R<br>
                   freq ( 59 - 59) =       3064.3  [cm-1]   -->
              A               I+R<br>
                   freq ( 60 - 60) =       3610.2  [cm-1]   -->
              A               I+R<br>
               </div>
            <div>Computer B gave</div>
            <div>     freq ( 46 - 46) =         33.0  [cm-1]   -->
              A               I+R<br>
                   freq ( 47 - 47) =         45.1  [cm-1]   -->
              A               I+R<br>
                   freq ( 48 - 48) =         54.1  [cm-1]   -->
              A               I+R<br>
                   freq ( 49 - 49) =         78.2  [cm-1]   -->
              A               I+R<br>
                   freq ( 50 - 50) =         82.4  [cm-1]   -->
              A               I+R<br>
                   freq ( 51 - 51) =         99.1  [cm-1]   -->
              A               I+R<br>
                   freq ( 52 - 52) =        108.9  [cm-1]   -->
              A               I+R<br>
                   freq ( 53 - 53) =        114.4  [cm-1]   -->
              A               I+R<br>
                   freq ( 54 - 54) =        188.3  [cm-1]   -->
              A               I+R<br>
                   freq ( 55 - 55) =        590.6  [cm-1]   -->
              A               I+R<br>
                   freq ( 56 - 56) =       1101.8  [cm-1]   -->
              A               I+R<br>
                   freq ( 57 - 57) =       1533.4  [cm-1]   -->
              A               I+R<br>
                   freq ( 58 - 58) =       2812.1  [cm-1]   -->
              A               I+R<br>
                   freq ( 59 - 59) =       3644.5  [cm-1]   -->
              A               I+R<br>
                   freq ( 60 - 60) =       3786.8  [cm-1]   -->
              A               I+R<br>
            </div>
            <div><br>
            </div>
            <div><span lang="EN-US"><font face="Times New Roman"
                  color="#0000ff"><b>Why the two computers give totally
                    different results? </b></font></span></div>
            <p style="margin:0cm 0cm 0pt;text-align:left" align="left"><font
                face="Times New Roman" color="#0000ff"><b><br>
                </b></font></p>
            <div><br>
            </div>
            <div> &CONTROL<br>
                               calculation = 'scf' ,<br>
                              restart_mode = 'from_scratch' ,<br>
                                    outdir = './' ,<br>
                                pseudo_dir = '/home/jibiaoli/pseudo/' ,<br>
                                    prefix = 'sym' ,<br>
                                   tstress = .true. ,<br>
                                   tprnfor = .true. ,<br>
               /<br>
               &SYSTEM<br>
                                     ibrav = 0,<br>
                                 celldm(1) = 9.456004324,<br>
                                       nat = 20,<br>
                                      ntyp = 3,<br>
                                   ecutwfc = 49 ,<br>
                                   ecutrho = 411 ,<br>
                               occupations = 'smearing' ,<br>
                                   degauss = 0.02 ,<br>
                                  smearing = 'methfessel-paxton' ,<br>
                                  vdw_corr = 'DFT-D',<br>
               /<br>
               &ELECTRONS<br>
                               mixing_beta = 0.3 ,<br>
                           diagonalization = 'david' ,<br>
               /<br>
              CELL_PARAMETERS alat <br>
                   0.866025404    0.500000000    0.000000000 <br>
                   0.866025404   -0.500000000    0.000000000 <br>
                   0.000000000    0.000000000    5.400000000 <br>
              ATOMIC_SPECIES<br>
                 Ag  107.8682  Ag.pbe-n-kjpaw_psl.1.0.0.UPF <br>
                  O   15.99940  O.pbe-n-kjpaw_psl.1.0.0.UPF <br>
                  H    1.00800  H.pbe-kjpaw_psl.1.0.0.UPF <br>
              ATOMIC_POSITIONS angstrom <br>
              O        5.986597700   0.051902808  11.800640138<br>
              H        6.530086903   0.896034963  11.935550794<br>
              H        6.519207423  -0.788895855  11.940829013<br>
              O        2.800029893   0.013830142  11.748050047<br>
              H        3.756125095   0.022425916  11.956803063<br>
              Ag      -0.454154628   0.136836718   9.568098196<br>
              Ag       5.307442766   0.123896111   9.577760992<br>
              Ag       2.445911493   0.129358587   9.587754292<br>
              Ag       2.920157088   1.499919274   7.139192063<br>
              Ag       1.485120252  -0.981971793   7.160426239<br>
              Ag       4.380244685  -0.987689704   7.134282475<br>
              Ag       2.889028971  -1.667975200   4.717759990    0  
              0   0<br>
              Ag       4.333537867   0.833997281   4.717759990    0  
              0   0<br>
              Ag       5.778055146  -1.667970358   4.717759990    0  
              0   0<br>
              Ag       0.000000000   0.000000000   2.358879995    0  
              0   0<br>
              Ag       5.778052352   0.000009682   2.358879995    0  
              0   0<br>
              Ag       2.889026176   0.000004841   2.358879995    0  
              0   0<br>
              Ag       2.889023381   1.667984881   0.000000000    0  
              0   0<br>
              Ag       1.444514485  -0.833987600   0.000000000    0  
              0   0<br>
              Ag       4.333540661  -0.833982759   0.000000000    0  
              0   0   <br>
              K_POINTS automatic <br>
                6 6 1   0 0 0 <br>
            </div>
            <div><br>
            </div>
            <div>phonons at Gamma<br>
               &inputph<br>
                tr2_ph=1.0d-14,<br>
                prefix='sym',<br>
                alpha_mix=0.1,<br>
                fildyn='phG.dyn',<br>
                amass(1)=107.8682,<br>
                amass(2)=15.999,<br>
                amass(3)=1.0079,<br>
                outdir='./'<br>
                nat_todo=5,<br>
               /<br>
              0.0 0.0 0.0<br>
              1 2 3 4 5<br>
              <br>
            </div>
            <div><br>
            </div>
            <div>
              <div style="color:rgb(144,144,144);font-family:Arial
                Narrow;font-size:12px">------------------</div>
              <div
                style="font-size:14px;font-family:Verdana;color:rgb(0,0,0)">
                <div><i><font size="2" face="Times New Roman"
                      color="#0000ff"><b>Dr. Jibiao Li, </b></font></i></div>
                <div><i><font size="2" face="Times New Roman"
                      color="#0000ff"><b>Department of Material Science
                        and Engineering</b></font></i></div>
                <div><i><font size="2" face="Times New Roman"
                      color="#0000ff"><b>Yangtze Normal University</b></font></i></div>
                <div><i><font face="Times New Roman"><font size="2"><font
                          color="#0000ff"><b><span
style="text-align:left;text-transform:none;line-height:21px;text-indent:0px;letter-spacing:normal;font-variant:normal;text-decoration:none;word-spacing:0px;display:inline;white-space:normal;float:none;background-color:transparent">Juxian
                              Dadao 16#,</span> Fuling, Chongqing, China</b></font></font></font></i></div>
                <div><i><font size="2" face="Times New Roman"
                      color="#0000ff"><b>Email: <a
                          href="mailto:jibiaoli@yznu.edu.cn"
                          target="_blank" moz-do-not-send="true">jibiaoli@yznu.edu.cn</a>,
                        <a href="mailto:jibiaoli@foxmail.com"
                          target="_blank" moz-do-not-send="true">jibiaoli@foxmail.com</a>,
                        <a href="mailto:jibiao.li@hotmail.com"
                          target="_blank" moz-do-not-send="true">jibiao.li@hotmail.com</a></b></font></i></div>
                <div><i><font size="2" face="Times New Roman"
                      color="#0000ff"><b>Homepage: <a
                          href="https://www.researchgate.net/profile/Jibiao_Li"
                          target="_blank" moz-do-not-send="true">https://www.researchgate.net/profile/Jibiao_Li</a></b></font></i></div>
              </div>
            </div>
            <div> </div>
            _______________________________________________<br>
            Quantum ESPRESSO is supported by MaX (<a
              href="http://www.max-centre.eu/quantum-espresso"
              target="_blank" rel="noreferrer" moz-do-not-send="true">www.max-centre.eu/quantum-espresso</a>)<br>
            users mailing list <a
              href="mailto:users@lists.quantum-espresso.org"
              target="_blank" moz-do-not-send="true">users@lists.quantum-espresso.org</a><br>
            <a
              href="https://lists.quantum-espresso.org/mailman/listinfo/users"
              target="_blank" rel="noreferrer" moz-do-not-send="true">https://lists.quantum-espresso.org/mailman/listinfo/users</a></blockquote>
        </div>
        <br clear="all">
        <br>
        -- <br>
        <div class="gmail_signature" dir="ltr">
          <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>
      </div>
      <br>
      <fieldset class="mimeAttachmentHeader"></fieldset>
      <pre class="moz-quote-pre" wrap="">_______________________________________________
Quantum ESPRESSO is supported by MaX (<a class="moz-txt-link-abbreviated" href="http://www.max-centre.eu/quantum-espresso">www.max-centre.eu/quantum-espresso</a>)
users mailing list <a class="moz-txt-link-abbreviated" href="mailto:users@lists.quantum-espresso.org">users@lists.quantum-espresso.org</a>
<a class="moz-txt-link-freetext" href="https://lists.quantum-espresso.org/mailman/listinfo/users">https://lists.quantum-espresso.org/mailman/listinfo/users</a></pre>
    </blockquote>
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