Try to reduce conv_thr to 1.d-12 and tr2_ph to 1.d-18. The cutoffs are pseudopotential dependent, I cannot comment on them. Yet, the most likely source of error is that you have used the an incorrect cell parameters and/or atomic coordinates.
kind regards Dr. Lorenzo Paulatto IdR @ IMPMC - CNRS UMR 7590 & Sorbonne Université phone: +33 (0)1 442 79822 / skype: paulatz http://www.impmc.upmc.fr/~paulatto/ (https://link.getmailspring.com/link/[email protected]/0?redirect=http%3A%2F%2Fwww.impmc.upmc.fr%2F~paulatto%2F&recipient=dXNlcnNAbGlzdHMucXVhbnR1bS1lc3ByZXNzby5vcmc%3D) - https://anharmonic.github.io/ (https://link.getmailspring.com/link/[email protected]/1?redirect=https%3A%2F%2Fanharmonic.github.io%2F&recipient=dXNlcnNAbGlzdHMucXVhbnR1bS1lc3ByZXNzby5vcmc%3D) 23-24/423 B115, 4 place Jussieu 75252 Paris CX 05 On Sep 22 2021, at 3:43 pm, Anupriya Nyayban <[email protected]> wrote: > I have calculated the phonon dispersion of orthorhombic RbPbI3 (Pnma) using > "PHONON" as implemented in Quantum Espresso and found the negative > frequencies ( which should not be present as suggested in > https://doi.org/10.1063/1.5131575 > (https://link.getmailspring.com/link/[email protected]/2?redirect=https%3A%2F%2Fdoi.org%2F10.1063%2F1.5131575&recipient=dXNlcnNAbGlzdHMucXVhbnR1bS1lc3ByZXNzby5vcmc%3D)). > It would be great help if you suggest to me where I am doing wrong!!! I have > provided the computational details below: > 1) The structure first is being relaxed and then the convergence tests are > performed for Ecut, Kmesh and Lattice parameters. > 2) Using the relaxed structure with converged parameters, SCF is performed > with cov_thr=1.0d-8 (ecutwfc=70, ecutrho=600, kmesh=12*6*3); phonon > calculation is performed with tr2_ph=1.0d-14 at Gamma point, frequencies are > obtained by imposing acoustic sum rule at the Gamma point with asr=simple. > > Thank you!! > > -- > With regards > Anupriya Nyayban > Ph.D. Scholar > Department of Physics > NIT Silchar > > > > > _______________________________________________ > Quantum ESPRESSO is supported by MaX (www.max-centre.eu) > users mailing list [email protected] > https://lists.quantum-espresso.org/mailman/listinfo/users
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