I'm not an expert of this specific calculation, but I suspect that the equation breaks down if even a tiny negative frequency is present. This because energy conservation between phonons and electrons would not be enforceable in a meaningful way. Sometimes, if the system has internal degrees of freedom, a very fine relax calculation can remove negative frequencies. Or if they arise from interpolation, changing the sum rule method.
-- Lorenzo Paulatto Written on a virtual keyboard with real fingers On 29 Jul 2017 10:15 a.m., "Isaiah Moses" <[email protected]> wrote: Dr Giovanni, Thanks a lot. I appreciate your response. We observed few values of frequencies to be negative. Matdyn1 has few more with others having either the first or the first 2/3 to be negative. We set those to be zero, modifying lambda.f90 code. Could that be the problem? I've attached the input/output for lambda.x execution. Also matdyn1 and 45. There are 62-points and 33 irreps. I appreciate your time. On Fri, Jul 28, 2017 at 12:17 PM, Isaiah Moses <[email protected]> wrote: > Here is lambda.in and out. > > On Fri, Jul 28, 2017 at 12:13 PM, Isaiah Moses <[email protected]> wrote: > >> Dr Giovanni, >> Thanks a lot. >> I appreciate your response. >> We observed few values of frequencies to be negative. >> Matdyn1 has few more with others having either the first or the first 2/3 >> to be negative. >> We set those to be zero, modifying lambda.f90 code. >> >> Could that be the problem? >> >> I've attached the input/output for lambda.x execution. Also matdyn1 and >> 45. >> >> There are 62-points and 33 irreps. >> I appreciate your time. >> >> Isaiah >> >> On Fri, Jul 28, 2017 at 10:41 AM, Giovanni Cantele < >> [email protected]> wrote: >> >>> Not that easy to answer without seeing relevant input/output files. >>> >>> As far as I know, Tc is quite difficult to converge. Did you made VERY >>> VERY VERY careful checks on convergence with >>> resect to ALL calculation parameters, starting from phonon frequencies? >>> >>> Giovanni >>> >>> >>> On 28 Jul 2017, at 11:37, Isaiah Moses <[email protected]> wrote: >>> >>> Dear everyone, >>> >>> I did an el-ph calculation of a monoclinic structure and am getting >>> really strange values of Tc . See the result below >>> lambda omega_log T_c >>> 0.00994 112.048 0.10012314E+08 >>> 0.03760 92.373 0.13380511E+10 >>> 0.07564 90.247 0.39802174E+19 >>> 0.09959 89.414 0.19865362E+78 >>> 0.11010 89.463 0.40671597-151 >>> 0.11454 90.329 0.16986711E-65 >>> 0.11678 92.320 0.99512429E-51 >>> 0.11772 94.657 0.29927798E-46 >>> 0.11744 97.141 0.16242032E-47 >>> 0.11619 99.442 0.65514785E-54 >>> >>> I'm wondering why such values. >>> >>> Any comment shall be greatly appreciated. >>> >>> Thanks, >>> Isaiah >>> >>> -- >>> Isaiah Abu Moses >>> Graduate Student, >>> Physics Department, >>> University of Ibadan, >>> Nigeria >>> >>> >>> >>> -- >>> Isaiah Abu Moses >>> Graduate Student, >>> Physics Department, >>> University of Ibadan, >>> Nigeria >>> _______________________________________________ >>> Pw_forum mailing list >>> [email protected] >>> http://pwscf.org/mailman/listinfo/pw_forum >>> >>> >>> -- >>> >>> Giovanni Cantele, PhD >>> CNR-SPIN >>> c/o Dipartimento di Fisica >>> Universita' di Napoli "Federico II" >>> Complesso Universitario M. S. Angelo - Ed. 6 >>> Via Cintia, I-80126, Napoli, Italy >>> e-mail: [email protected] >>> Phone: +39 081 676910 <+39%20081%20676910> >>> Skype contact: giocan74 >>> >>> ResearcherID: http://www.researcherid.com/rid/A-1951-2009 >>> Web page: http://people.fisica.unina.it/~cantele >>> >>> >>> _______________________________________________ >>> Pw_forum mailing list >>> [email protected] >>> http://pwscf.org/mailman/listinfo/pw_forum >>> >> >> >> >> -- >> Isaiah Abu Moses >> Graduate Student, >> Physics Department, >> University of Ibadan, >> Nigeria >> > > > > -- > Isaiah Abu Moses > Graduate Student, > Physics Department, > University of Ibadan, > Nigeria > -- Isaiah Abu Moses Graduate Student, Physics Department, University of Ibadan, Nigeria _______________________________________________ Pw_forum mailing list [email protected] http://pwscf.org/mailman/listinfo/pw_forum
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