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> 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 > 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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