<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; color: rgb(0, 0, 0); font-size: 14px; font-family: Arial, sans-serif;"><div><div><div>Dear all,</div></div></div><div><br></div><div>I am working on hydrogen trapping in a tungsten vacancy.</div><ul><li>I first create a vacancy in a 3x3x3 supercell that I optimize,</li><li>Then I trap a H atom inside, then I relax the system,</li><li>I further need to know the phonon frequencies of the hydrogen atom to compute thermodynamic properties.</li></ul><div>Due to the mass difference between H and W, the phonon modes associated to H are assumed to be decoupled from the W ones. So the only H phonon modes are calculated at the gamma point.</div><div><br></div><div>My question is about dynmat.x. Should I use it or not ?</div><div><br></div><div>As recommended in the phonon tutorial file (<a href="http://www.quantum-espresso.org/wp-content/uploads/2013/06/phonons_tutorial_shanghai1.pdf">http://www.quantum-espresso.org/wp-content/uploads/2013/06/phonons_tutorial_shanghai1.pdf</a>) I run dynmat.x routine after the phonon calculation.</div><div><br></div><div>Dynamt.x is designed to impose the acoustic sum rule to the acoustic modes. But in my case there are no acoustic modes since all the W atoms are fixed. The problem is that H frequencies look like very different with and without dynmat.x.</div><div><br></div><div>So my question, what are the correct ones ?</div><div><br></div><div>I attach below:</div><div>The inputs w3_vac_HOh_ph.in w3_vac_HOh_dynmat.in and outputs w3_vac_HOh_ph.out, w3_vac_HOh_dynmat.out of the phonon calculation.</div><div><br></div><div><br></div><div>Many thank you for your help</div><div><br></div><div><div><div><div>====================================================================</div><div>Nicolas Fernandez, PhD student</div><div>Equipe de Spectrométrie et Dynamique Moléculaire</div><div>Laboratoire de Physique des Interaction Ioniques et Moléculaire (PIIM)</div><div>UMR-CNRS 7345, Aix Marseille Université</div><div>Campus de St Jérôme, Service 252 </div><div>13397 Marseille Cedex 20</div></div><div><br></div></div></div></body></html>