Location

Portland State University, Portland, Oregon

Start Date

12-5-2015 9:00 AM

End Date

12-5-2015 10:30 AM

Subjects

Crystallography, Bicrystallography

Description

Three dimensional (3D) bicrystallography describes ideal structures of grain boundaries comprehensively at the atomic level as a function of the five macroscopic and two of the four microscopic parameters [1,2]. Free energy minimization of these structures leads to the real structure of these topologically distinct regions within crystals. These minimizations may either reduce the symmetries of ideal bicrystals or leave them intact. Since the symmetries of physical properties need to be compatible (by the Shubnikov-Curie and Curie-Minnigerode-Neumann principles [3]) with the symmetries of the atomic arrangements from which they arise, bicrystallography allows for predictions about which phenomena can occur in the 3D regions around grain boundaries. Because it provides atomically resolved (real space) images, the most popular structure analysis technique for grain boundaries [2] is Transmission Electron Microscopy (TEM). Since this is a projection technique, there is a need for the development of bicrystallography in two dimensions in order to make sense of TEM images in a straightforward way. We utilized a graphical procedure for 2D bicrystallography recently in the analysis of coincidence site lattice boundaries with [001] tilt axis in all cubic holohedral materials and present this procedure in this contribution in a didactic manner. We also reproduce from ref. [4] (with permission by the publisher) pairs of predicted and experimentally observed Σ13a (510) boundaries in SrTiO3 that are related by grain boundary migration, Fig. 1, in order to illustrate both the predictive power and the limitations of the bicrystallography approach.

Persistent Identifier

http://archives.pdx.edu/ds/psu/19807

2D bicrystallography for SRS 2015 Andrew (1).doc (1244 kB)
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May 12th, 9:00 AM May 12th, 10:30 AM

Bicrystallography in two dimensions: A graphical procedure and comparison of its results to experiments

Portland State University, Portland, Oregon

Three dimensional (3D) bicrystallography describes ideal structures of grain boundaries comprehensively at the atomic level as a function of the five macroscopic and two of the four microscopic parameters [1,2]. Free energy minimization of these structures leads to the real structure of these topologically distinct regions within crystals. These minimizations may either reduce the symmetries of ideal bicrystals or leave them intact. Since the symmetries of physical properties need to be compatible (by the Shubnikov-Curie and Curie-Minnigerode-Neumann principles [3]) with the symmetries of the atomic arrangements from which they arise, bicrystallography allows for predictions about which phenomena can occur in the 3D regions around grain boundaries. Because it provides atomically resolved (real space) images, the most popular structure analysis technique for grain boundaries [2] is Transmission Electron Microscopy (TEM). Since this is a projection technique, there is a need for the development of bicrystallography in two dimensions in order to make sense of TEM images in a straightforward way. We utilized a graphical procedure for 2D bicrystallography recently in the analysis of coincidence site lattice boundaries with [001] tilt axis in all cubic holohedral materials and present this procedure in this contribution in a didactic manner. We also reproduce from ref. [4] (with permission by the publisher) pairs of predicted and experimentally observed Σ13a (510) boundaries in SrTiO3 that are related by grain boundary migration, Fig. 1, in order to illustrate both the predictive power and the limitations of the bicrystallography approach.