Bloch states at different k are orthogonal because they have different k, not because their periodic parts are orthogonal, so your test is not a valid one. Note that you have to take into account the different ordering of plane waves (array igk) at k and k' when computing <k| something |k'>
P. On Thu, 2013-10-31 at 02:13 -0400, Bo Qiu wrote: > Dear developers and users, > > > I'm trying to compute some matrix elements between states k and k'. To > confirm my calculation, I first try to compute the overlap between > wavefunction k and k' as < k| k'> in quantum espresso by taking zdoc > of state k and k' (modified the elphonon.f90 code). I do find for the > same k point, the overlap between different bands are 0. However, the > overlap between two states at different points k and k' are almost > always non-zero, indicating they're not orthogonal. I thought in > theory they should all be orthonormal because they belong to the same > Hamiltonian of the entire system. So is it because of numerical > reasons that they're actually not orthogonal in quantum espresso? > > > Thanks a lot for you help! > > > Bo > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://pwscf.org/mailman/listinfo/pw_forum -- Paolo Giannozzi, Dept. Chemistry&Physics&Environment, Univ. Udine, via delle Scienze 208, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222
