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Scaling Relations For Dislocation Structure And Response, Richard Alan Lesar, M. Koslowski, Robb Thomson, J. M. Rickman
Scaling Relations For Dislocation Structure And Response, Richard Alan Lesar, M. Koslowski, Robb Thomson, J. M. Rickman
Richard Alan Lesar
A major goal in dislocation theory is the development of a coarse-grained method that would enable predictions of dislocation response without resolving the degrees of freedom of all the dislocations. While a number of possible coarse-grained theories have been proposed, all of these need information about structures at scales smaller than the coarse-graining volume. Here we present results from dislocation simulations that yield scaling relations with the hope that they can provide a framework for modeling the sub-scale dislocation structures and dynamics. For example, we show that dislocations have a self-similar (fractal) structure over wide range of stress/strain; dislocations move …
Theoretical Prediction Of New High-Performance Lead-Free Piezoelectrics, Pio Baettig, Charles F. Schelle, Richard Alan Lesar, Umesh V. Waghmare, Nicola A. Spaldin
Theoretical Prediction Of New High-Performance Lead-Free Piezoelectrics, Pio Baettig, Charles F. Schelle, Richard Alan Lesar, Umesh V. Waghmare, Nicola A. Spaldin
Richard Alan Lesar
We predict the occurrence of large ferroelectric polarization and piezoelectricity in the hypothetical perovskite-structure oxides, bismuth aluminate (BiAlO3) and bismuth gallate (BiGaO3), using density functional theory within the local density approximation. We show that BiGaO3 will have a similar structure to PbTiO3, although with much stronger tetragonal distortion and therefore improved ferroelectric properties. Likewise, BiAlO3 shares structural characteristics with antiferrodistortive PbZrO3, but it is also a ferroelectric with large polarization. Therefore, we propose the Bi(Al,Ga)O3 system as a replacement for the widely used piezoelectric material, Pb(Zr,Ti)O3 (PZT), that will avoid the environmental toxicity problems of lead-based compounds. Finally, we show …