<div dir="ltr">Dear Paolo<div><br></div><div>Thank you for your detailed explanation</div><div><br></div><div><p>I recalculated the phonon dispersion using a smaller energy cutoff and coarser k-point mesh, and I noticed that the anomalous oscillations around the Gamma and A points disappeared. However, I now have a new question regarding the dielectric tensor values.</p>
<p>Using QE v.6.4.1 with
ecutwfc = 100 and 15x15x12 k-mesh I obtained <strong>+725.22</strong> for both the xx and yy components of the dielectric tensor.<br>
Using QE v.7.3, with the same cutoff and k-mesh, I instead obtained <strong>-48192.85</strong> for both components.</p><p>Finally, using
QE v.7.3, with ecutwfc = 80 and 12x12x9 k-mesh, the values changed to <strong>+1102.27</strong>.</p>
<p>I am trying to understand the cause of these large discrepancies, especially the negative and extremely large values in the second case.</p>
<p>Any insights would be greatly appreciated.</p>
<p>Best regards,</p></div><div><br></div><div><br></div></div><br><div class="gmail_quote gmail_quote_container"><div dir="ltr" class="gmail_attr">El jue, 5 jun 2025 a las 9:57, Paolo Giannozzi (<<a href="mailto:paolo.giannozzi@uniud.it">paolo.giannozzi@uniud.it</a>>) escribió:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Hi<br>
<br>
I don't know the reasons for the weird behavior with v.7.3. If you have <br>
split your calculation into partial one, that could be the reason <br>
(sometimes the "splitting" machinery does not work as expected).<br>
I could reproduce your results with v.6.4.1, though. If you look at the <br>
output (or dynamical matrix file) for q=0, you will notice very large <br>
values for the dielectric tensor along xx and yy. This indicates a <br>
quasi-metallic character of your system, presumably as a consequence of <br>
DFT shortcomings, spin-orbit interactions absence, or both. If you <br>
replace in the dynamical matrix files the dielectric tensor with the <br>
experimental one (exx = eyy = 14.4, ezz = 13.1) and re-compute the force <br>
constant matrices, the anomalous behaviour at q => 0 disappears.<br>
<br>
Thanks to Pietro Delugas and Lorenzo Paulatto for help on this subject.<br>
<br>
Paolo<br>
<br>
On 01/06/2025 01:07, Ivan Dario Arellano Ramirez wrote:<br>
> <br>
> Hi QE users<br>
> <br>
> Recently, I performed phonon calculations using the ph.x module <br>
> implemented in QE. I initially used the version 6.4.1 and obtained the <br>
> results shown in the attached figure (top). I noticed an <br>
> unusual behavior near the gamma point, one of the acoustic branches <br>
> exhibits a U-shaped anomaly with some negative frequencies (small <br>
> values). The acoustic modes should approach the Gamma point linearly.<br>
> <br>
> After some time, I decided to repeat the calculations using identical <br>
> input file parameters, but on a different machine and with QE version <br>
> 7.3. In this version, the band structures shows oscillations around both <br>
> the gamma and A points.<br>
> <br>
> Could anyone help me understand the origin of these two issues:<br>
> 1) in the top figure, v.6.4.1 the anomalous U-shape of one of the <br>
> acoustic branches near the gamma point.<br>
> 2) In v. 7.3, the oscillations around the gamma and A points.<br>
> <br>
> Any insights or suggestions would be appreciated<br>
> <br>
> Here are the <a href="http://ph.in" rel="noreferrer" target="_blank">ph.in</a> <<a href="http://ph.in" rel="noreferrer" target="_blank">http://ph.in</a>>, <a href="http://q2r.in" rel="noreferrer" target="_blank">q2r.in</a> <<a href="http://q2r.in" rel="noreferrer" target="_blank">http://q2r.in</a>>, <a href="http://matdyn.in" rel="noreferrer" target="_blank">matdyn.in</a> <br>
> <<a href="http://matdyn.in" rel="noreferrer" target="_blank">http://matdyn.in</a>><br>
> <br>
> Phonons of InN at G!=0<br>
> &inputph<br>
> tr2_ph = 1.0d-14,<br>
> ldisp = .true.,<br>
> search_sym = .false.,<br>
> prefix = 'inn-ph',<br>
> recover = .true.<br>
> fildyn = 'inn-ph.dyn',<br>
> nq1 = 5,<br>
> nq2 = 5,<br>
> nq3 = 3,<br>
> amass(1) = 114.818,<br>
> amass(2) = 14.007,<br>
> outdir = './tmp'<br>
> /<br>
> <br>
> &INPUT<br>
> fildyn = 'inn-ph.dyn',<br>
> zasr = 'crystal'<br>
> flfrc = 'inn-ph.fc'<br>
> /<br>
> <br>
> &input<br>
> asr = 'crystal',<br>
> flfrc = 'inn-ph.fc',<br>
> flfrq = 'inn.band.freq'<br>
> flvec = 'inn.band.modes'<br>
> amass(1) = 114.818,<br>
> amass(2) = 14.007,<br>
> q_in_band_form = .true.<br>
> /<br>
> 8<br>
> 0.0000000000 0.0000000000 0.0000000000 40 ! Gamma<br>
> 0.5000000000 0.0000000000 0.0000000000 25 ! M<br>
> 0.3333333333 0.3333333333 0.0000000000 40 ! K<br>
> 0.0000000000 0.0000000000 0.0000000000 25 ! Gamma<br>
> 0.0000000000 0.0000000000 0.5000000000 40 ! A<br>
> 0.5000000000 0.0000000000 0.5000000000 25 ! L<br>
> 0.3333333333 0.3333333333 0.5000000000 40 ! H<br>
> 0.0000000000 0.0000000000 0.5000000000 1 ! A<br>
> <br>
> Regards,<br>
> <br>
> -- <br>
> <br>
> Iván Darío Arellano Ramírez<br>
> <br>
> Profesor Titular Programa de Ingeniería Física<br>
> <br>
> Director Grupo de Investigación en Modelado y Simulación Computacional<br>
> <br>
> Universidad Tecnológica de Pereira<br>
> <br>
> <br>
> El contenido de este mensaje y sus anexos son únicamente para el uso del <br>
> destinatario y pueden contener información clasificada o reservada. Si <br>
> usted no es el destinatario intencional, absténgase de cualquier uso, <br>
> difusión, distribución o copia de esta comunicación.<br>
> <br>
> _______________________________________________________________________________<br>
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<br>
-- <br>
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,<br>
Univ. Udine, via delle Scienze 206, 33100 Udine Italy, +39-0432-558216<br>
<br>
</blockquote></div><div><br clear="all"></div><div><br></div><span class="gmail_signature_prefix">-- </span><br><div dir="ltr" class="gmail_signature"><div dir="ltr"><div dir="ltr"><div><div><p class="MsoNormal" style="background-image:initial;background-position:initial;background-repeat:initial"><span style="font-family:Arial,sans-serif">Iván Darío Arellano Ramírez</span></p>
<p class="MsoNormal" style="background-image:initial;background-position:initial;background-repeat:initial"><span style="font-family:Arial,sans-serif">Profesor Titular Programa de Ingeniería Física</span></p>
<p class="MsoNormal" style="background-image:initial;background-position:initial;background-repeat:initial"><span style="font-family:Arial,sans-serif">Director Grupo de Investigación en Modelado y Simulación Computacional</span></p>
<p class="MsoNormal" style="text-align:justify"><span style="font-family:Arial,sans-serif;background-image:initial;background-position:initial;background-repeat:initial">Universidad
Tecnológica de Pereira</span><span lang="RU"></span></p></div></div></div></div></div>
<br>
<span style="font-family:arial,sans-serif;font-size:12.8px;text-align:justify;background-color:rgb(255,255,255)">El contenido de este mensaje y sus anexos son únicamente para el uso del destinatario y pueden contener información clasificada o reservada. Si usted no es el destinatario intencional, absténgase de cualquier uso, difusión, distribución o copia de esta comunicación.</span>