[Q-e-developers] Integration of EPW into QE 5

[Samuel Poncé]

Dear Paolo,

Fair point ! Thank you.

Actually the sum of the modes of the electron-phonon matrix elements were
different in the two EPW, then I moved on to compare the two QE quantity
and focused on the irr. modes.

I still think that they should be the same but the fact that their sum is
the same is good enough for me.

I think I found the bug in EPW thanks to your help and have now the same
matrix elements for that q-point.

Thank you again !

Best,

Samuel





2015-06-29 20:21 GMT+01:00 Paolo Giannozzi <paolo.giannozzi at uniud.it>:

> On Mon, Jun 29, 2015 at 8:34 PM, Samuel Poncé <samuel.pon at gmail.com>
> wrote:
>
> 1) replace only set_irr.f90 and random_matrix.f90 with the previous
>> versions
>> elphmat(:,:,:)**2  0.1192375
>> elphmat(:,:,:)**2  0.9861288
>> elphmat(:,:,:)**2  1.354492
>> elphmat(:,:,:)**2  0.3075966
>>
>> We get the old behaviour. Therefore only changing those two routines
>> solves it ... but:
>>
>> 2 ) remove the "arg = randy(0)" line
>>
>> elphmat(:,:,:)**2  0.1192376
>> elphmat(:,:,:)**2  0.9861288
>> elphmat(:,:,:)**2  1.419427
>> elphmat(:,:,:)**2  0.2426619
>>
>> 3)in set_irr.f90
>> arg = randy(987654321)
>>
>> elphmat(:,:,:)**2  0.1192376
>> elphmat(:,:,:)**2  0.9861287
>> elphmat(:,:,:)**2  1.522261
>> elphmat(:,:,:)**2  0.1398291
>>
>> 4 ) in set_irr.f90
>> call set_rndm_seed(1)
>>
>
> no: "call set_random_seed ()", a different one
>
>
>> but keep randy in random_matrix.f90
>>
>> elphmat(:,:,:)**2  0.1192375
>> elphmat(:,:,:)**2  0.9861287
>> elphmat(:,:,:)**2  1.419427
>> elphmat(:,:,:)**2  0.2426619
>>
>
> the same as "randy(0)", since this is (I think) the default behavior of
> randy if a seed is not set.
>
>>
>> As you can see the last two elements only are affected. Actually the two
>> first one corresponds to irreducible modes that are non-degenerate and the
>> two last one are irreducible with two degenerate modes (the sum of the
>> degenerate mode should be fine though...).
>>
>
> wait  a minute:  the sum of the degenerate mode looks fine to me
>    1.354492+0.3075966=1.6620886
>    1.419427+0.2426619=1.6620889
>    1.522261+0.1398291=1.6620901
> and what you found earlier:
>    1.348592+0.3134982=1.6620902
> Once again: are you really sure that EACH of the above terms should not
> depend upon the specific irrep? degenerate irreps span a well-defined
> subspace but the specific choice of irreps will have an unpredictable phase
>
> Paolo
>
> --
> Paolo Giannozzi, Dept. Chemistry&Physics&Environment,
> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
> Phone +39-0432-558216, fax +39-0432-558222
>
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