[QE-users] question about wave functions phonon code

[Jacopo Simoni]

So this means the phase factor is of the form e^{iG(k)r} where G(k) is the
translation vector in rec. space such that
G(k)+q+k=q'+k' (inside the first Brillouin zone)
the phase factor is therefore dependent on the k vector and in reciprocal
space the wave functions of the two equivalent q points are shifted by the
vector G(k) ?
Is there a variable in the code corresponding to this vector G or to the
phase factor itself ?


On Sat, 25 Sept 2021 at 03:42, Paolo Giannozzi <p.giannozzi at gmail.com>
wrote:

> On Sat, Sep 25, 2021 at 2:00 AM Jacopo Simoni via users <
> users at lists.quantum-espresso.org> wrote:
>
> This wave function appears different from the wave function at an
>> equivalent q point, for instance if I look at evq at q=(0,0,1), this is
>> different from evq at (1,1,0) that are equivalent by translation of a G
>> vector (I am thinking here at a FCC periodic lattice). The two functions
>> just differ by a phase factor or I am missing something ?
>>
>
> They differ by a phase factor; moreover, in the presence of degenerate
> eigenvalues, you have no guarantee that the eigenvectors in the degenerate
> subspace are the same. Finally, the ordering of k+G components is not
> necessarily the same in the two cases
>
> Paolo
>
> Thanks in advance,
>> Jacopo Simoni, Lawrence Berkeley National Lab.
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>
>
> --
> Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
> Univ. Udine, via delle Scienze 206, 33100 Udine, Italy
> Phone +39-0432-558216, fax +39-0432-558222
>
>
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