Dear Paolo Thank you for your detailed explanation
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. Using QE v.6.4.1 with ecutwfc = 100 and 15x15x12 k-mesh I obtained *+725.22* for both the xx and yy components of the dielectric tensor. Using QE v.7.3, with the same cutoff and k-mesh, I instead obtained *-48192.85* for both components. Finally, using QE v.7.3, with ecutwfc = 80 and 12x12x9 k-mesh, the values changed to *+1102.27*. I am trying to understand the cause of these large discrepancies, especially the negative and extremely large values in the second case. Any insights would be greatly appreciated. Best regards, El jue, 5 jun 2025 a las 9:57, Paolo Giannozzi (<[email protected]>) escribió: > Hi > > I don't know the reasons for the weird behavior with v.7.3. If you have > split your calculation into partial one, that could be the reason > (sometimes the "splitting" machinery does not work as expected). > I could reproduce your results with v.6.4.1, though. If you look at the > output (or dynamical matrix file) for q=0, you will notice very large > values for the dielectric tensor along xx and yy. This indicates a > quasi-metallic character of your system, presumably as a consequence of > DFT shortcomings, spin-orbit interactions absence, or both. If you > replace in the dynamical matrix files the dielectric tensor with the > experimental one (exx = eyy = 14.4, ezz = 13.1) and re-compute the force > constant matrices, the anomalous behaviour at q => 0 disappears. > > Thanks to Pietro Delugas and Lorenzo Paulatto for help on this subject. > > Paolo > > On 01/06/2025 01:07, Ivan Dario Arellano Ramirez wrote: > > > > Hi QE users > > > > Recently, I performed phonon calculations using the ph.x module > > implemented in QE. I initially used the version 6.4.1 and obtained the > > results shown in the attached figure (top). I noticed an > > unusual behavior near the gamma point, one of the acoustic branches > > exhibits a U-shaped anomaly with some negative frequencies (small > > values). The acoustic modes should approach the Gamma point linearly. > > > > After some time, I decided to repeat the calculations using identical > > input file parameters, but on a different machine and with QE version > > 7.3. In this version, the band structures shows oscillations around both > > the gamma and A points. > > > > Could anyone help me understand the origin of these two issues: > > 1) in the top figure, v.6.4.1 the anomalous U-shape of one of the > > acoustic branches near the gamma point. > > 2) In v. 7.3, the oscillations around the gamma and A points. > > > > Any insights or suggestions would be appreciated > > > > Here are the ph.in <http://ph.in>, q2r.in <http://q2r.in>, matdyn.in > > <http://matdyn.in> > > > > Phonons of InN at G!=0 > > &inputph > > tr2_ph = 1.0d-14, > > ldisp = .true., > > search_sym = .false., > > prefix = 'inn-ph', > > recover = .true. > > fildyn = 'inn-ph.dyn', > > nq1 = 5, > > nq2 = 5, > > nq3 = 3, > > amass(1) = 114.818, > > amass(2) = 14.007, > > outdir = './tmp' > > / > > > > &INPUT > > fildyn = 'inn-ph.dyn', > > zasr = 'crystal' > > flfrc = 'inn-ph.fc' > > / > > > > &input > > asr = 'crystal', > > flfrc = 'inn-ph.fc', > > flfrq = 'inn.band.freq' > > flvec = 'inn.band.modes' > > amass(1) = 114.818, > > amass(2) = 14.007, > > q_in_band_form = .true. > > / > > 8 > > 0.0000000000 0.0000000000 0.0000000000 40 ! Gamma > > 0.5000000000 0.0000000000 0.0000000000 25 ! M > > 0.3333333333 0.3333333333 0.0000000000 40 ! K > > 0.0000000000 0.0000000000 0.0000000000 25 ! Gamma > > 0.0000000000 0.0000000000 0.5000000000 40 ! A > > 0.5000000000 0.0000000000 0.5000000000 25 ! L > > 0.3333333333 0.3333333333 0.5000000000 40 ! H > > 0.0000000000 0.0000000000 0.5000000000 1 ! A > > > > Regards, > > > > -- > > > > Iván Darío Arellano Ramírez > > > > Profesor Titular Programa de Ingeniería Física > > > > Director Grupo de Investigación en Modelado y Simulación Computacional > > > > Universidad Tecnológica de Pereira > > > > > > 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. > > > > > _______________________________________________________________________________ > > The Quantum ESPRESSO Foundation stands in solidarity with all civilians > worldwide who are victims of terrorism, military aggression, and > indiscriminate warfare. > > > -------------------------------------------------------------------------------- > > Quantum ESPRESSO is supported by MaX (www.max-centre.eu) > > users mailing list [email protected] > > https://lists.quantum-espresso.org/mailman/listinfo/users > > -- > Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche, > Univ. Udine, via delle Scienze 206, 33100 Udine Italy, +39-0432-558216 > > -- Iván Darío Arellano Ramírez Profesor Titular Programa de Ingeniería Física Director Grupo de Investigación en Modelado y Simulación Computacional Universidad Tecnológica de Pereira -- 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.
_______________________________________________________________________________ The Quantum ESPRESSO Foundation stands in solidarity with all civilians worldwide who are victims of terrorism, military aggression, and indiscriminate warfare. -------------------------------------------------------------------------------- Quantum ESPRESSO is supported by MaX (www.max-centre.eu) users mailing list [email protected] https://lists.quantum-espresso.org/mailman/listinfo/users
