Hello Daniel, Thanks for your answer. I have the value for z=0: P = 0.0000049 (mod 14.7398000) (e/Omega).bohr
Pascal > Le 27 févr. 2018 à 07:09, Daniel Stoeffler > <daniel.stoeff...@ipcms.unistra.fr> a écrit : > > Hello Pascal, > > Don't forget the polarization quantum : the jump at z=0.5 looks like coming > from a quantum of polarization and can be removed (I mean by adding 1 to your > numbers for z > 0.5). In principle, variation of P should remain small > between points on your path. > > Why don't you have the value for z=0 ? > > Best wishes, > > Daniel > > > > Le 2018-02-26 22:13, pboulet a écrit : > >> Dear all, >> >> Does anyone have tried to used Jiang, Levchenko and Rappe’s method to >> calculate oxidation state of atoms? (Phys. Rev Letters, 108, 2012, 166403. >> >> In brief, the formula is N=V/e \Delta(P) x R /R^2, >> where N, V, e, \Delta(P) and R are the oxidation state, cell volume, >> electron charge, change in polarisation and lattice vector, respectively. >> \Delta(P) x R corresponds to the dot product. >> The idea is just to displace an atom along a path traversing the cell in a >> way that the atom goes from its location to that in the next cell. >> >> I have tried with the PbTiO3 example of QE for the calculation of >> polarization via the Berry phase. If I am right I should obtain +2 as an >> oxidation state. >> >> I have displaced the Pb atom (crystal position at 0. 0. 0.) along the z axis >> from 0 to 1. >> >> The enclosed picture depicts N versus z for z=0..1. I used the polarization >> P given by QE in units of (e/Omega).bohr, since it is similar to the formula >> above. >> I have just divided P by z since Delta(P) and R are collinear… and I guess >> V/e of the formula cancels with e/Omega… I am not sure of these assumptions, >> however… >> >> First the variation is -2 instead of +2. In addition the evolution is not >> smooth and the missing points on the curve are calculated to be negative. I >> have removed them but it is nonsense to me. >> >> Does anyone know what is wrong? >> >> Thank you for your suggestions, >> >> Pascal >> >> >> >> >> >> >> >> >> >> >> >> Pascal Boulet >> — >> Professor in computational chemistry - DEPARTMENT OF CHEMISTRY >> Director of the Madirel laboratory >> Aix-Marseille University - Avenue Escadrille Normandie Niemen - F-13013 >> Marseille - FRANCE >> Tél: +33(0)4 13 55 18 10 et +33(0)4 13 55 18 19 - Fax : +33(0)4 13 55 18 50 >> Email : pascal.bou...@univ-amu.fr <mailto:pascal.bou...@univ-amu.fr> >> >> >> >> >> >> _______________________________________________ >> Pw_forum mailing list >> Pw_forum@pwscf.org <mailto:Pw_forum@pwscf.org> >> http://pwscf.org/mailman/listinfo/pw_forum >> <http://pwscf.org/mailman/listinfo/pw_forum> > _______________________________________________ > Pw_forum mailing list > Pw_forum@pwscf.org > http://pwscf.org/mailman/listinfo/pw_forum
_______________________________________________ Pw_forum mailing list Pw_forum@pwscf.org http://pwscf.org/mailman/listinfo/pw_forum
