(110) and (001), sorry. These are both X points, equivalent under translation (the dynamical matrix is the same also I checked in the code).
On Mon, 27 Sept 2021 at 12:25, Stefano Baroni <[email protected]> wrote: > 100 is not equivalent to 110 in FCC … SB > > ___ > Stefano Baroni, Trieste -- http://stefano.baroni.me > > On 27 Sep 2021, at 19:55, Jacopo Simoni via users < > [email protected]> wrote: > > > Hi thanks for the reply. I need to compute a sort of finite temperature > electron-phonon coupling, so I needed to go into the code and I wrote my > own routine to do that, I am debugging the code and I noticed that the > result at different but equivalent q points, let's say X=(1,0,0) and > X=(1,1,0) in FCC are not the same as I should expect. > Then I noticed that the wave function (evq) in reciprocal space differs > (that is expected) but I do not understand the relation between the two, > that was why I was asking the previous question. In the meantime I found a > mistake in the way I was computing the potential derivative, that is > probably the main source of my problem. I was wondering also what does the > routine symdyn_munu_new exactly do? Why does the dynamical matrix have to > be symmetrized in the basis of the modes ? > > Thanks in advance, > Jacopo Simoni, Lawrence Berkeley National Lab. > > On Mon, 27 Sept 2021 at 00:20, Lorenzo Paulatto <[email protected]> wrote: > >> Hello Jacopo, >> instead of answering your question, I may ask you what you actually want >> to do, because chances are that your problem has already been met by others. >> >> E.g. there are ways to eliminate this phase, or to neutralize it to >> compute the derivative w.r.t. the wave vector. But more often, when you >> have an observable quantity that comes from a sum over the k-points, the >> phases will cancel out in the total, if done correctly. It is actually a >> good way to check that your formulas are correct. >> >> Hth >> >> -- >> Lorenzo Paulatto >> >> On Sat, Sep 25, 2021, 21:28 Jacopo Simoni via users < >> [email protected]> wrote: >> >>> 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 <[email protected]> >>> wrote: >>> >>>> On Sat, Sep 25, 2021 at 2:00 AM Jacopo Simoni via users < >>>> [email protected]> 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. >>>>> _______________________________________________ >>>>> Quantum ESPRESSO is supported by MaX (www.max-centre.eu) >>>>> users mailing list [email protected] >>>>> https://lists.quantum-espresso.org/mailman/listinfo/users >>>> >>>> >>>> >>>> -- >>>> 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 >>>> >>>> _______________________________________________ >>> Quantum ESPRESSO is supported by MaX (www.max-centre.eu) >>> users mailing list [email protected] >>> https://lists.quantum-espresso.org/mailman/listinfo/users >> >> _______________________________________________ > Quantum ESPRESSO is supported by MaX (www.max-centre.eu) > users mailing list [email protected] > https://lists.quantum-espresso.org/mailman/listinfo/users > >
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