Polarization is defined modulo a polarization quantum. Note the "(mod 0.3458)" in the output: the two numbers you mention differ by (almost exactly) two times that factor
Paolo On Mon, Sep 7, 2015 at 5:00 PM, Francesco Pelizza < [email protected]> wrote: > Hi dear Users, > > I am experiencing the event where the total polarization of the material I > am studying (PVDF), do not always give the same outcome if I change the > number of atoms, switching from the normal cell to a super cell containing > more atoms than the minimum. > > Is always the same with the same atomic model, but is not if I change the > model !! > > Here attached you can find the input file and output file of the two > atomistic models. The first is made with 12 atoms, the second with 24, but > is always PVDF in the same crystal phase, the Beta one. > > in the 12 atoms model I have a result of 0.5231 C/M^2 > in the 24 atoms model I have a result of -0.1683 C/M^2 > > > Actually, I am not fully sure if I get wrong with the berry phase > calculation settings, or I am ignoring some important aspects of the > software and or the calculation that justify this, and I have to learn how > to interpret the results? > > I tested QE on my machine with pervoskites and nothing goes wrong, the > results of the essential atomic models fully agree with literature. > > Can you give me a hand in understanding why this is happening? > > Thank you very much to anyone !!! > > Francesco Pelizza > > PhD student, Starthclyde, Glasgow, Scotland > > > > _______________________________________________ > Pw_forum mailing list > [email protected] > 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
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