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11:00
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Ferroelectric
Properties of BaxSr1-xTiO3 Solid Solutions from
Molecular
Dynamics Simulations
Silvia
Tinte
National
Institute of Standard and Technology
The current keen
interest in solid solution of perovskite ferroelectrics is driven by the desire
to create structures with properties unachievable in single-component
materials. BaxSr1-xTiO3 (BST), a solid solution of BaTiO3 and
SrTiO3, exists for the whole concentration range and is a mixture of a
ferroelectric with an incipient ferroelectric. In this material, the
phase transitions, usually sharp in single-component perovskite, are
much more diffuse as evidenced by the rather broad peak in the
temperature dependence of the dielectric constant, and the origin
of which is not well understood. We have developed classical
shell-model potentials for describing the complex ferroelectric
behavior of the single components BaTiO3 and SrTiO3, and used them to
simulate the BST solid solution. The temperature versus composition
phase diagram is very well described and the local behavior of the
structure and polarization is analyzed. We show that the
ferroelectric properties of the BST solid solution can be understood in
terms of the effects of average density and the local chemical
environment. The experimentally observed static dielectric peak
broadening around Tc at low "x" is reproduced in the simulation and
seems to be related to the average volume rather than to the local
chemical environment.
Biographical Sketch
Dr. Silvia Tinte
received her Ph.D. in 2001 from the National University of Rosario, Argentina,
and then worked as a post doctorate at Rutgers
University, NJ, with
Professor Rabe and Vanderbilt. She is currently a postdoc at the National
Institute of Standard and Technology (NIST), MD. Her research is
focused on the theoretical investigation of ferroelectric
materials. Dr. Tinte has extensive experience using
first-principles methods both directly and in the construction of
indirect method as atomistic shell models and effective Hamiltonians
for the prediction and analysis of properties of single compounds and
solid solutions, in bulk and thin film forms.