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Ab Initio Molecular Dynamics Simulations of the Ferroelectric-Paraelectric Phase Transition in Sodium Nitrite

preprint
submitted on 14.02.2019 and posted on 14.02.2019 by Johannes P. Dürholt, Rochus Schmid
This paper reports on the first ab initio molecular dynamics study of the ferroelectric Sodium Nitrite, shedding light on its order-disorder phase transition. The remnant polarization Pr was calculated using a Mulliken population analysis and maximally localized Wannier functions. Especially the Wannier based model is in excellent agreement with experimental findings and previous Berry phase calculations. The simulations predict a ferroelectric Curie temperature Tc between 400 K and 450 K in good agreement with the experimental value of 437 K. In addition, the anomalous lattice behavior (shrinking of the c-axis) during the phase transition is reproduced. The crystal field effect in the material could be quantified by investigating the molecular dipoles based on the maximally localized Wannier functions and the intermolecular charge transfer by analysing the Mulliken charges. In agreement with earlier experimental and theoretical findings, the polarization reversal mechanism was found to be dominated by a c-axis rotation of the Nitrite ions. The molecular insight into such a simple and prototypical material serves as a basis for a further development of more complex crystalline order-disorder ferroelectrics.

Funding

Coordination Funds

Deutsche Forschungsgemeinschaft

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History

Email Address of Submitting Author

johannes.duerholt@rub.de

Institution

Ruhr-Universität Bochum

Country

Germany

ORCID For Submitting Author

0000-0002-3494-1621

Declaration of Conflict of Interest

No

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