符徳勝
2015/09/09 1:39、nilofar hadaeghi <n.hadae...@gmail.com> のメッセージ: > I really appreciate your help. > I4/mcm is centrosymmetric. I studied the tutorial related to GaN and it > helped me very much. So I conclude to calculate the difference in > polarization, two structures that at least one of them should not be > centrosymmetric are needed, Is it correct? > Would you please guide me whether it is allowed to calculate the difference > in polarization between a strained and unstrained state of a system by > implementing the berryPI on each of them separately and then subtract them ?! > if it going to, what does the derived polarization describe?! > Piezoelectricity(since it is the difference in polarization caused by strain) > or spontaneous polarization? > Best regards, > >> On Tue, Sep 8, 2015 at 5:07 AM, Oleg Rubel <oru...@lakeheadu.ca> wrote: >> That seems to be the case >> (http://www.cryst.ehu.es/cgi-bin/cryst/programs/nph-wp-list?gnum=140). >> If both structures possess the inversion symmetry, it will be pointless to >> calculate polarization. >> >> Oleg >> >> > On Sep 8, 2015, at 03:48, Fecher, Gerhard <fec...@uni-mainz.de> wrote: >> > >> > I thought that I4/mcm is also a centrosymmetric space group ? >> > >> > Ciao >> > Gerhard >> > >> > DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy: >> > "I think the problem, to be quite honest with you, >> > is that you have never actually known what the question is." >> > >> > ==================================== >> > Dr. Gerhard H. Fecher >> > Institut of Inorganic and Analytical Chemistry >> > Johannes Gutenberg - University >> > 55099 Mainz >> > and >> > Max Planck Institute for Chemical Physics of Solids >> > 01187 Dresden >> > ________________________________________ >> > Von: wien-boun...@zeus.theochem.tuwien.ac.at >> > [wien-boun...@zeus.theochem.tuwien.ac.at] im Auftrag von Oleg Rubel >> > [oru...@lakeheadu.ca] >> > Gesendet: Dienstag, 8. September 2015 01:03 >> > An: A Mailing list for WIEN2k users >> > Betreff: Re: [Wien] berryPI >> > >> > The essence of electronic polarization is that it is a “relative” >> > quantity, i.e., its calculation (and measurement too) requires a reference >> > point. The reference structure is not always centrosymmetric. An example >> > of non-centrosymmetric reference structure is zinc-blende GaN that is >> > taken as P=0 in computing the spontaneous polarization of the wurtzite GaN >> > (see >> > https://github.com/spichardo/BerryPI/wiki/Tutorial-4:-Polarization-in-GaN). >> > >> > For the second part of the question on EuTiO3, enclosed structure files >> > would certainly help. One possible strategy would be to explore a gradual >> > evolution of the polarization between cubic and tetragonal structures. >> > >> > >> > I hope this will help >> > Oleg >> > >> > >> > >> >> On Sep 7, 2015, at 3:42 AM, nilofar hadaeghi <n.hadae...@gmail.com> wrote: >> >> >> >> Dear all >> >> I have studied some papers whose authors are S.J.Ahmed or O.Rubel in >> >> which building the centrosymmetric and noncentrosymmetric structure for >> >> the calculation of spontaneous polarization has been explained, but it is >> >> still ambiguous for me. >> >> Could you please help me whether the noncentrosymmetric structure must >> >> exist in the nature or it is enough to apply a displacement to the >> >> central atom of the centrosymmetric structure and then use the new >> >> structure as the noncentrosymmetric one?! >> >> For instance I am working on EuTiO3 in which a structural transition at >> >> temperature 282(k) from cubic to tetragonal ( from Pm3m space group to >> >> I4/mcm) occurs. Now, would you please help me whether I use the structure >> >> in I4/mcm space group as the noncentrosymmetric structure or I must >> >> change the positions of the centrosymmetric structure and use the >> >> achieved structure as the noncentrosymmetric one? >> >> I am using WIEN2k 14.2, Python version: 2.7.3 and Numpy version: 1.6.2. >> >> Sincerely yours, >> >> _______________________________________________ >> >> Wien mailing list >> >> Wien@zeus.theochem.tuwien.ac.at >> >> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien >> >> SEARCH the MAILING-LIST at: >> >> http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html >> > >> > _______________________________________________ >> > Wien mailing list >> > Wien@zeus.theochem.tuwien.ac.at >> > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien >> > SEARCH the MAILING-LIST at: >> > http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html >> > _______________________________________________ >> > Wien mailing list >> > Wien@zeus.theochem.tuwien.ac.at >> > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien >> > SEARCH the MAILING-LIST at: >> > http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html >> >> _______________________________________________ >> Wien mailing list >> Wien@zeus.theochem.tuwien.ac.at >> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien >> SEARCH the MAILING-LIST at: >> http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html > > _______________________________________________ > Wien mailing list > Wien@zeus.theochem.tuwien.ac.at > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > SEARCH the MAILING-LIST at: > http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html
_______________________________________________ Wien mailing list Wien@zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at: http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html
