[Pw_forum] Strange Values of Tc

[Lorenzo Paulatto]

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
>>>
>>>
>>> _______________________________________________
>>> Pw_forum mailing list
>>> Pw_forum at pwscf.org
>>> 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

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