[Pw_forum] Strange Values of Tc

[Isaiah Moses]

Dear Lorenzo,
I appreciate your very useful comment.
Effort is being made to ensure non negative frequencies.

Thanks a lot,
Isaiah

On Sat, Jul 29, 2017 at 10:50 AM, Lorenzo Paulatto <
lorenzo.paulatto at impmc.upmc.fr> wrote:

> 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" <imoses87 at gmail.com> 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 <imoses87 at gmail.com> wrote:
>
>> Here is lambda.in and out.
>>
>> On Fri, Jul 28, 2017 at 12:13 PM, Isaiah Moses <imoses87 at gmail.com>
>> 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 <
>>> giovanni.cantele at spin.cnr.it> 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 <imoses87 at gmail.com> 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
>>>> Pw_forum at pwscf.org
>>>> 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: giovanni.cantele at spin.cnr.it
>>>> 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
>>>>
>>>>
>>>> _______________________________________________
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>>>>
>>>
>>>
>>>
>>> --
>>> 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
>
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>
>
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>



-- 
Isaiah Abu Moses
Graduate Student,
Physics Department,
University of Ibadan,
Nigeria
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