Dear Sheikh Jamil Ahmed I also think that the point of the PhysRevLett.97.267602 is exactly what you referred. Of course previously in Phys. Rev. B *85*, 104109, three candidate ground state had been identified but in PhysRevLett.97.267602, I4/mcm space group has been mentioned as the ground state, and I think Dr. Gerhard's purpose was making this point clear that calculating the polarization using I4/mcm space group is meaningless!
On Wed, Sep 9, 2015 at 3:32 PM, nilofar hadaeghi <n.hadae...@gmail.com> wrote: > Dear Fecher, Gerhard > your recommended papers have been carefully studied. > I understood that in this compound, different structural phases whether > for the unstrained or strained states can be occurred among which just > the ones whose space groups are not centrosymmetric would be meaningful to > be used in calculating the polarization. For instance in the strained > state, it has been allowed to calculate the polarization for the space > group P4mm. and not I4/mcm The relation between the oxygen octahedra > tilting and the low energy symmetry is still unknown. > Thank you for your attention. > > > > > > > > > > > > > > > > . > > On Wed, Sep 9, 2015 at 2:52 PM, nilofar hadaeghi <n.hadae...@gmail.com> > wrote: > >> Dear Pleg Rubel and Sheikh Jamil Ahmed >> I really appreciate your attention and guidance. I was really >> confused and you helped me a lot. >> Best regards, >> N.Hadaeghi >> >> >> On Wed, Sep 9, 2015 at 2:24 AM, Fecher, Gerhard <fec...@uni-mainz.de> >> wrote: >> >>> If you check Figure 2 of PhysRevLett.109.267602, you will find that >>> there is NO polarization in I4/mcm ! >>> and in the PhysRevLett.97.267602 you find "... the crystallographic >>> symmetry becomes P4/mm", now compare this to the Fig.2 of the first >>> reference, what do you see ? >>> >>> >>> 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 Sheikh Jamil >>> Ahmed [sahm...@lakeheadu.ca] >>> Gesendet: Dienstag, 8. September 2015 23:06 >>> An: A Mailing list for WIEN2k users >>> Betreff: Re: [Wien] berryPI >>> >>> I would like to add that EuTiO3 seems to be a multiferroic compound with >>> ground state being antiferromagnetic- paraelectric system (I4/mcm). Then, >>> under some compressive or tensile epitaxial strain, several types of >>> transition is possible (For example, antiferromagnetic- ferroelectric or >>> ferromagnetic- ferroelectric) depending on the magnitude and type of >>> strain. The following articles address this issue very well. >>> http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.109.267602 >>> >>> http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.97.267602 >>> >>> >>> Hope that helps. >>> >>> Sheikh >>> >>> -- >>> Sheikh Jamil Ahmed >>> PhD Student >>> Department of Material Science and Engineering >>> McMaster University >>> 1280 Main Street West >>> Hamilton, Ontario, Canada L8S 4L7 >>> >>> >>> On Tue, Sep 8, 2015 at 3:07 PM, Oleg Rubel <oru...@lakeheadu.ca<mailto: >>> oru...@lakeheadu.ca>> wrote: >>> To address your questions... >>> >>> > 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? >>> >>> That’s correct. When the structure file contains the inversion symmetry, >>> Wien2k switches from complex to real version for wave functions. Then there >>> is no phase information to be processed. >>> >>> > 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? >>> >>> You are heading towards piezoelectric coefficients. There are some >>> technicalities, such as clamped vs relaxed ion approximation, proper vs >>> improper. Here is a good reference: >>> http://arxiv.org/pdf/cond-mat/9903137.pdf >>> I do not see any barriers from BerryPI perspective. >>> >>> >>> Best regards >>> Oleg >>> >>> _______________________________________________ >>> Wien mailing list >>> Wien@zeus.theochem.tuwien.ac.at<mailto: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 >>> >> >> >
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