Modelling and Designing Ferroelectrics with Defects and in Two-dimensional Forms Laurent Bellaiche, University of Arka

1. Modelling and Designing Ferroelectrics with Defects and in Two-dimensional Forms Laurent Bellaiche, University of Arkansas, DMR 0404335 Ferroelectric thin films are of increasing interest due to their unique potential for the next generation of functional nanoscale devices with superior properties. The most important issue in such devices is how to control the polarization (which arises from the formation of electric dipoles). First-principles calculations confirmed a recent, exciting experimental finding, namely that such polarization can be manipulated by deforming the ferroelectric film on a picosecond time scale. These first-principles simulations also provided the microscopic origin of this anomalous dynamical coupling between polarization and picosecond time-scale strain pulses, that is a ``slow breathing’’ of dipolar inhomogeneities. [Phys. Rev. Lett. 101, 197602 (2008)] Snapshots at different times of the dipole pattern in a ferroelectric film subject to an ultrafast strain pulse. A nanobubble (in which the dipoles are along a direction opposite to that of the dipoles located outside this nanobubble) changes its size, which is the discovered process allowing an unusual control of polarization.

2. Modelling and Designing Ferroelectrics with Defects and in Two-dimensional Forms Laurent Bellaiche, University of Arkansas, DMR 0404335 • Broader impact: • 6 graduate students (including two of female gender) and 7 research associates (including two of female gender) contributed to the works associated with this grant. • Mrs Laura Walizer received her Ph.D. of Physics in Spring 2009. • Dr. Inna Ponomareva became Assistant Professor at The University of South Florida in Spring 2009. • Collaborations with international groups, and strongly involving students and research associates, occurred. • The P.I. spent one day with students in an elementary school in Fall 2008. • The P.I.’s group and collaborators gave several invited talks at international conferences. • An invited review article on complex dipolar structures was written and published in a special issue of Journal of Materials Science.