Re: [Pw_forum] Phonon negative Frequency
Dear All, Thank you all for your kind reply. >From all of your reply, I understood one could not know negative frequency while the phonon program is running till it's end whether it is running in parallel mode or in serial mode. I also understand one has to take precautions while running phonon calculation like reducing convergence value than normal and doing the phonon calculation for any specific q-point. I will run the program as you all suggested and report to the forum. Thank you Yours Sincerly, A.Suresh, Research Scholar, School of Physics, Madurai Kamaraj University, Madurai. ___ Pw_forum mailing list Pw_forum@pwscf.org http://pwscf.org/mailman/listinfo/pw_forum
Re: [Pw_forum] Phonon negative Frequency
Dear Suresh, Adding to the comment of Isaiah, did you check the FAQ? http://www.quantum-espresso.org/faq/phonons/#7.3 Greetings, apsi PS Why running in serial...? I guess basically any CPU nowadays has at least two cores. -=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=- Ari Paavo Seitsonen / ari.p.seitso...@iki.fi / http://www.iki.fi/~apsi/ Ecole Normale Supérieure (ENS), Département de Chimie, Paris Mobile (F) : +33 789 37 24 25(CH) : +41 79 71 90 935 On Wed, 29 Nov 2017, Isaiah Moses wrote: Dear Suresh, I doubt if there is any way you can know if you'll have negative frequency while the calculation is on. However you can take note of some of the information in phonon user's guide on how to avoid negative frequency. Also, you can do a test run with a single q-point splitted among irreps in order to save your time and computational resources. Check example on how to split phonon calculation in case you are not familiar with that. All the best, Isaiah. On Wed, Nov 29, 2017 at 6:24 AM, Suresh A wrote: Dear All, I am ran phonon calculation for anatase previously and got negative frequencies. I was install QE-5.2.0 in serial mode and took days to finish the calculation in my desktop. Is there any way to know the negative frequency before the calculation ends? So that the time can be saved. Thank You Yours Sincerly, A.Suresh, Research Scholar, School of Physics, Madurai Kamaraj University, Madurai. ___ Pw_forum mailing list Pw_forum@pwscf.org http://pwscf.org/mailman/listinfo/pw_forum -- Isaiah Abu Moses Graduate Student, Physics Department, University of Ibadan, Nigeria ___ Pw_forum mailing list Pw_forum@pwscf.org http://pwscf.org/mailman/listinfo/pw_forum
Re: [Pw_forum] Phonon negative Frequency
Hi1- Use parallel version2- A bad converged structure (with low threshold) may give large negative phonons.3- Use very tight SCF convergence Regards David On Wednesday, November 29, 2017, 10:42:44 AM GMT+3:30, Suresh A wrote: Dear All, I am ran phonon calculation for anatase previously and got negative frequencies. I was install QE-5.2.0 in serial mode and took days to finish the calculation in my desktop. Is there any way to know the negative frequency before the calculation ends? So that the time can be saved. Thank You Yours Sincerly, A.Suresh, Research Scholar, School of Physics, Madurai Kamaraj University, Madurai. ___ Pw_forum mailing list Pw_forum@pwscf.org http://pwscf.org/mailman/listinfo/pw_forum ___ Pw_forum mailing list Pw_forum@pwscf.org http://pwscf.org/mailman/listinfo/pw_forum
Re: [Pw_forum] Phonon negative Frequency
Dear Suresh, unfortunately, there is no way to know this before - or at least I don't know of any. Yet, you'll nearly always have 3 negative frequencies at the Gamma point which should actually be zero. Furthermore, it is really important that you relax your system really carefully before attempting a phonon calculation - in fact, you should also decrease the convergence threshold for the scf from the standard 1.D-6 to maybe 1.D-8. Kind regards Thomas On 29.11.2017 06:24, Suresh A wrote: Dear All, I am ran phonon calculation for anatase previously and got negative frequencies. I was install QE-5.2.0 in serial mode and took days to finish the calculation in my desktop. Is there any way to know the negative frequency before the calculation ends? So that the time can be saved. Thank You Yours Sincerly, A.Suresh, Research Scholar, School of Physics, Madurai Kamaraj University, Madurai. ___ Pw_forum mailing list Pw_forum@pwscf.org http://pwscf.org/mailman/listinfo/pw_forum -- Dr. rer. nat. Thomas Brumme Wilhelm-Ostwald-Institute for Physical and Theoretical Chemistry Leipzig University Phillipp-Rosenthal-Strasse 31 04103 Leipzig Tel: +49 (0)341 97 36456 email: thomas.bru...@uni-leipzig.de ___ Pw_forum mailing list Pw_forum@pwscf.org http://pwscf.org/mailman/listinfo/pw_forum
Re: [Pw_forum] Phonon negative Frequency
Dear Suresh, I doubt if there is any way you can know if you'll have negative frequency while the calculation is on. However you can take note of some of the information in phonon user's guide on how to avoid negative frequency. Also, you can do a test run with a single q-point splitted among irreps in order to save your time and computational resources. Check example on how to split phonon calculation in case you are not familiar with that. All the best, Isaiah. On Wed, Nov 29, 2017 at 6:24 AM, Suresh A wrote: > Dear All, > I am ran phonon calculation for anatase previously and got > negative frequencies. I was install QE-5.2.0 in serial mode and took days > to finish the calculation in my desktop. > > Is there any way to know the negative frequency before the calculation > ends? So that the time can be saved. > Thank You > > Yours Sincerly, > > A.Suresh, > Research Scholar, > School of Physics, > Madurai Kamaraj University, > Madurai. > > ___ > Pw_forum mailing list > Pw_forum@pwscf.org > http://pwscf.org/mailman/listinfo/pw_forum > -- Isaiah Abu Moses Graduate Student, Physics Department, University of Ibadan, Nigeria ___ Pw_forum mailing list Pw_forum@pwscf.org http://pwscf.org/mailman/listinfo/pw_forum
[Pw_forum] Phonon negative Frequency
Dear All, I am ran phonon calculation for anatase previously and got negative frequencies. I was install QE-5.2.0 in serial mode and took days to finish the calculation in my desktop. Is there any way to know the negative frequency before the calculation ends? So that the time can be saved. Thank You Yours Sincerly, A.Suresh, Research Scholar, School of Physics, Madurai Kamaraj University, Madurai. ___ Pw_forum mailing list Pw_forum@pwscf.org http://pwscf.org/mailman/listinfo/pw_forum
