This is defenetly late responce but in order to keep information there is a reason for responce. I don't know units in CP2K output, but CP2K save Hessian in unformatted bynary file, which can be easily read and then diagonalized. The sqrt of eigenvalues is freqeuncy of vibrational modes wich can be converted to cm-1 by factor multiplying, where the factor is:<div>sqrt(Hartree/AMU/Bohr2Angstrom)*1/2/pi/Angstrom/c*sqrt(massunit/Bohr2Angstrom)/1)10**5</div><div>Hartree=4.359748536313086e-18</div><div>AMU=1.6605402e-27</div><div>Bohr2Angstrom=0.529177207423948</div><div>massunit=a_mass/e_mass</div><div>a_mass=1.660538782e-27</div><div>e_mass=9.10938215e-31</div><div>I've wrote convertor from cp2k hessian file format to FORCE_CONSTANTS file format (see attachment). Using PHONOPY one can write dynamical matrix, plot eigenvectors and lot of other things. <br><br></div><div>Best wishes,<br>Eugene</div><div class="gmail_quote"><div dir="auto" class="gmail_attr">среда, 10 июня 2020 г. в 16:56:53 UTC+3, tfjer...@gmail.com: <br/></div><blockquote class="gmail_quote" style="margin: 0 0 0 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;"><div dir="ltr">Dear all, <div><br></div><div>I would like to use TAMkin (<a href="http://molmod.github.io/tamkin/" target="_blank" rel="nofollow" data-saferedirecturl="https://www.google.com/url?hl=ru&q=http://molmod.github.io/tamkin/&source=gmail&ust=1637150482457000&usg=AFQjCNFxlyqYfUvf5XbBi2fxn_Tzu09AJQ">http://molmod.github.io/tamkin/</a>) to compute thermodynamic properties from the vibrational frequencies computed with CP2K.</div><div>As I have understood it, the way TAMkin works is to read and diagonalize the Hessian matrix printed in the CP2K output.</div><div>When I compare the frequencies obtained with TAMkin with those obtained with cp2k, the values are not the same (Compare column 2 and 3 in the table below). </div><div><br></div><div>The first task is then to understand how CP2K computes the frequencies. To investigate this, I copied the Hessian matrix from the CP2K output (printed below the string "Hessian in cartesian coordinates") and pasted it into Excel and saved it as a csv file. This file I read into python and diagonalized the Hessian with numpy. The frequencies I get are different from those printed in the cp2k output file (compare column 3 and 4 in the  table below). </div><div>I have assumed that the units of the Hessian matrix in the cp2k output file are Ry*bohr-2*kamu-1 (kamu = 1000*amu). This assumption is based on trial and error; it was what got me closest to the cp2k frequencies. </div><div><br></div><div><br></div><div>Table 1: The eight lowest frequencies. There are 48 in total.</div><div><table border="1" cellspacing="0" cellpadding="0" style="border-collapse:collapse;border-width:initial;border-style:none">
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  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">frequencies</span><u></u><u></u></p>
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  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">TAMkin / <br>
  cm-1<u></u><u></u></span></p>
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  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">cp2k / <br>
  cm-1<u></u><u></u></span></p>
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  <td width="151" valign="top" style="width:4cm;border-top:1pt solid windowtext;border-right:1pt solid windowtext;border-bottom:1pt solid windowtext;border-left-width:initial;border-left-style:none;padding:0cm 5.4pt;height:30pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">Diag., cp2k Hessian / <br>
  cm-1<u></u><u></u></span></p>
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  <td width="85" nowrap valign="top" style="width:63.8pt;border-right:1pt solid windowtext;border-bottom:1pt solid windowtext;border-left:1pt solid windowtext;border-top-width:initial;border-top-style:none;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">1<u></u><u></u></span></p>
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  <td width="75" nowrap valign="top" style="width:56.45pt;border-top-width:initial;border-style:none solid solid none;border-left-width:initial;border-bottom-width:1pt;border-bottom-color:windowtext;border-right-width:1pt;border-right-color:windowtext;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">31.1<u></u><u></u></span></p>
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  <td width="76" nowrap valign="top" style="width:2cm;border-top-width:initial;border-style:none solid solid none;border-left-width:initial;border-bottom-width:1pt;border-bottom-color:windowtext;border-right-width:1pt;border-right-color:windowtext;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">27.3<u></u><u></u></span></p>
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  <td width="151" nowrap valign="top" style="width:4cm;border-top-width:initial;border-style:none solid solid none;border-left-width:initial;border-bottom-width:1pt;border-bottom-color:windowtext;border-right-width:1pt;border-right-color:windowtext;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">32.6<u></u><u></u></span></p>
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 </tr>
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  <td width="85" nowrap valign="top" style="width:63.8pt;border-right:1pt solid windowtext;border-bottom:1pt solid windowtext;border-left:1pt solid windowtext;border-top-width:initial;border-top-style:none;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">2<u></u><u></u></span></p>
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  <td width="75" nowrap valign="top" style="width:56.45pt;border-top-width:initial;border-style:none solid solid none;border-left-width:initial;border-bottom-width:1pt;border-bottom-color:windowtext;border-right-width:1pt;border-right-color:windowtext;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">38.3<u></u><u></u></span></p>
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  <td width="76" nowrap valign="top" style="width:2cm;border-top-width:initial;border-style:none solid solid none;border-left-width:initial;border-bottom-width:1pt;border-bottom-color:windowtext;border-right-width:1pt;border-right-color:windowtext;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">40.8<u></u><u></u></span></p>
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  <td width="151" nowrap valign="top" style="width:4cm;border-top-width:initial;border-style:none solid solid none;border-left-width:initial;border-bottom-width:1pt;border-bottom-color:windowtext;border-right-width:1pt;border-right-color:windowtext;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">40.1<u></u><u></u></span></p>
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  <td width="85" nowrap valign="top" style="width:63.8pt;border-right:1pt solid windowtext;border-bottom:1pt solid windowtext;border-left:1pt solid windowtext;border-top-width:initial;border-top-style:none;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">3<u></u><u></u></span></p>
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  <td width="75" nowrap valign="top" style="width:56.45pt;border-top-width:initial;border-style:none solid solid none;border-left-width:initial;border-bottom-width:1pt;border-bottom-color:windowtext;border-right-width:1pt;border-right-color:windowtext;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">47.7<u></u><u></u></span></p>
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  <td width="76" nowrap valign="top" style="width:2cm;border-top-width:initial;border-style:none solid solid none;border-left-width:initial;border-bottom-width:1pt;border-bottom-color:windowtext;border-right-width:1pt;border-right-color:windowtext;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">51.0<u></u><u></u></span></p>
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  <td width="151" nowrap valign="top" style="width:4cm;border-top-width:initial;border-style:none solid solid none;border-left-width:initial;border-bottom-width:1pt;border-bottom-color:windowtext;border-right-width:1pt;border-right-color:windowtext;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">50.2<u></u><u></u></span></p>
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 </tr>
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  <td width="85" nowrap valign="top" style="width:63.8pt;border-right:1pt solid windowtext;border-bottom:1pt solid windowtext;border-left:1pt solid windowtext;border-top-width:initial;border-top-style:none;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">4<u></u><u></u></span></p>
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  <td width="75" nowrap valign="top" style="width:56.45pt;border-top-width:initial;border-style:none solid solid none;border-left-width:initial;border-bottom-width:1pt;border-bottom-color:windowtext;border-right-width:1pt;border-right-color:windowtext;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">74.7<u></u><u></u></span></p>
  </td>
  <td width="76" nowrap valign="top" style="width:2cm;border-top-width:initial;border-style:none solid solid none;border-left-width:initial;border-bottom-width:1pt;border-bottom-color:windowtext;border-right-width:1pt;border-right-color:windowtext;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">74.0<u></u><u></u></span></p>
  </td>
  <td width="151" nowrap valign="top" style="width:4cm;border-top-width:initial;border-style:none solid solid none;border-left-width:initial;border-bottom-width:1pt;border-bottom-color:windowtext;border-right-width:1pt;border-right-color:windowtext;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">78.2<u></u><u></u></span></p>
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  <td width="85" nowrap valign="top" style="width:63.8pt;border-right:1pt solid windowtext;border-bottom:1pt solid windowtext;border-left:1pt solid windowtext;border-top-width:initial;border-top-style:none;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">5<u></u><u></u></span></p>
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  <td width="75" nowrap valign="top" style="width:56.45pt;border-top-width:initial;border-style:none solid solid none;border-left-width:initial;border-bottom-width:1pt;border-bottom-color:windowtext;border-right-width:1pt;border-right-color:windowtext;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">82.0<u></u><u></u></span></p>
  </td>
  <td width="76" nowrap valign="top" style="width:2cm;border-top-width:initial;border-style:none solid solid none;border-left-width:initial;border-bottom-width:1pt;border-bottom-color:windowtext;border-right-width:1pt;border-right-color:windowtext;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">80.0<u></u><u></u></span></p>
  </td>
  <td width="151" nowrap valign="top" style="width:4cm;border-top-width:initial;border-style:none solid solid none;border-left-width:initial;border-bottom-width:1pt;border-bottom-color:windowtext;border-right-width:1pt;border-right-color:windowtext;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">85.8<u></u><u></u></span></p>
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 </tr>
 <tr style="height:15.0pt">
  <td width="85" nowrap valign="top" style="width:63.8pt;border-right:1pt solid windowtext;border-bottom:1pt solid windowtext;border-left:1pt solid windowtext;border-top-width:initial;border-top-style:none;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">6<u></u><u></u></span></p>
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  <td width="75" nowrap valign="top" style="width:56.45pt;border-top-width:initial;border-style:none solid solid none;border-left-width:initial;border-bottom-width:1pt;border-bottom-color:windowtext;border-right-width:1pt;border-right-color:windowtext;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">111.0<u></u><u></u></span></p>
  </td>
  <td width="76" nowrap valign="top" style="width:2cm;border-top-width:initial;border-style:none solid solid none;border-left-width:initial;border-bottom-width:1pt;border-bottom-color:windowtext;border-right-width:1pt;border-right-color:windowtext;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">109.9<u></u><u></u></span></p>
  </td>
  <td width="151" nowrap valign="top" style="width:4cm;border-top-width:initial;border-style:none solid solid none;border-left-width:initial;border-bottom-width:1pt;border-bottom-color:windowtext;border-right-width:1pt;border-right-color:windowtext;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">116.3<u></u><u></u></span></p>
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 </tr>
 <tr style="height:15.0pt">
  <td width="85" nowrap valign="top" style="width:63.8pt;border-right:1pt solid windowtext;border-bottom:1pt solid windowtext;border-left:1pt solid windowtext;border-top-width:initial;border-top-style:none;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">7<u></u><u></u></span></p>
  </td>
  <td width="75" nowrap valign="top" style="width:56.45pt;border-top-width:initial;border-style:none solid solid none;border-left-width:initial;border-bottom-width:1pt;border-bottom-color:windowtext;border-right-width:1pt;border-right-color:windowtext;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">223.7<u></u><u></u></span></p>
  </td>
  <td width="76" nowrap valign="top" style="width:2cm;border-top-width:initial;border-style:none solid solid none;border-left-width:initial;border-bottom-width:1pt;border-bottom-color:windowtext;border-right-width:1pt;border-right-color:windowtext;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">224.1<u></u><u></u></span></p>
  </td>
  <td width="151" nowrap valign="top" style="width:4cm;border-top-width:initial;border-style:none solid solid none;border-left-width:initial;border-bottom-width:1pt;border-bottom-color:windowtext;border-right-width:1pt;border-right-color:windowtext;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">234.3<u></u><u></u></span></p>
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 </tr>
 <tr style="height:15.0pt">
  <td width="85" nowrap valign="top" style="width:63.8pt;border-right:1pt solid windowtext;border-bottom:1pt solid windowtext;border-left:1pt solid windowtext;border-top-width:initial;border-top-style:none;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">8<u></u><u></u></span></p>
  </td>
  <td width="75" nowrap valign="top" style="width:56.45pt;border-top-width:initial;border-style:none solid solid none;border-left-width:initial;border-bottom-width:1pt;border-bottom-color:windowtext;border-right-width:1pt;border-right-color:windowtext;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">245.6<u></u><u></u></span></p>
  </td>
  <td width="76" nowrap valign="top" style="width:2cm;border-top-width:initial;border-style:none solid solid none;border-left-width:initial;border-bottom-width:1pt;border-bottom-color:windowtext;border-right-width:1pt;border-right-color:windowtext;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">246.3<u></u><u></u></span></p>
  </td>
  <td width="151" nowrap valign="top" style="width:4cm;border-top-width:initial;border-style:none solid solid none;border-left-width:initial;border-bottom-width:1pt;border-bottom-color:windowtext;border-right-width:1pt;border-right-color:windowtext;padding:0cm 5.4pt;height:15pt">
  <p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal"><span lang="IT">257.3<u></u><u></u></span></p>
  </td>
 </tr>
</tbody></table></div><div><br></div><div>What is wrong with my calculation?</div><div>What steps should be done to go from the Hessian to the frequencies?</div><div><br></div><div>The Hessian in csv format, the python script and the cp2k output file are attached. </div><div><br></div><div>Thanks a lot for your help.</div><div><br></div><div>Regards,</div><div>Torstein Fjermestad</div><div> </div><div><br></div><div><br></div></div></blockquote></div>

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