Dear Paolo Thanks for reply.
Bests 2016-06-10 15:55 GMT+03:00 Paolo Giannozzi <[email protected]>: > See 5.0.0.19 and 5.0.0.20 in the user guide of PWscfs: > > http://www.quantum-espresso.org/wp-content/uploads/Doc/pw_user_guide/node20.html#SECTION000600190000000000000 > in particular this: > > * they contain a fractional translation that is incompatible with the > FFT grid (see next paragraph). Note that if you change cutoff or unit > cell volume, the automatically computed FFT grid changes, and this may > explain changes in symmetry (and in the number of k-points as a > consequence) for no apparent good reason (only if you have fractional > translations in the system, though). > [...] > > 5.0.0.20 Warning: symmetry operation # N not allowed > > This is not an error. If a symmetry operation contains a fractional > translation that is incompatible with the FFT grid, it is discarded in > order to prevent problems with symmetrization. Typical fractional > translations are 1/2 or 1/3 of a lattice vector. If the FFT grid > dimension along that direction is not divisible respectively by 2 or > by 3, the symmetry operation will not transform the FFT grid into > itself. Solution: you can either force your FFT grid to be > commensurate with fractional translation (set variables nr1, nr2, nr3 > to suitable values), or set variable use_all_frac to .true., in > namelist &SYSTEM. Note however that the latter is incompatible with > hybrid functionals and with phonon calculations. > > On Fri, Jun 10, 2016 at 1:58 PM, Bahadır SALMANKURT > <[email protected]> wrote: > > Dear All, > > > > I have been calculating structure parameter of ZrBeSi type crystal, whose > > point group is D6_h. When I take ecutrho as 500 Ry, everything is ok. But > > When I decrease ecutrho from 500 to 480 , its point group become D3_d > even > > if crystal_sg is used. > > > > Why does such a thing happen? > > > > Thanks in advance > > -- > > > > Bahadır SALMANKURT > > Ph.D. Candidate > > Department of Physics, Sakarya University, TURKEY > > > > _______________________________________________ > > Pw_forum mailing list > > [email protected] > > http://pwscf.org/mailman/listinfo/pw_forum > > > > -- > Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche, > Univ. Udine, via delle Scienze 208, 33100 Udine, Italy > Phone +39-0432-558216, fax +39-0432-558222 > > _______________________________________________ > Pw_forum mailing list > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum -- Bahadır SALMANKURT Ph.D. Candidate Department of Physics, Sakarya University, TURKEY
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