Dear Gerhard, If I understand correctly, the assumption about the structures of EuTiO3 in PhysRevLett.97.267602 is not accurate enough. The only consider the ground state to be Pm3_m and then do a compression study with P4/mm. PhysRevLett.109.267602 on the other hand pointed that the structure of bulk EuTiO3 in ground state should be I4/mcm. Then, under compression the transition goes from I4/mcm to I4cm to P4mm.
Sheikh On Wed, Sep 9, 2015 at 5:24 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://firstname.lastname@example.org/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://email@example.com/index.html >
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