Centrality measures highlight proton traps and access points to proton highways in kinetic Monte Carlo trajectories

Abstract

A centrality measure based on the time of first returns rather than the number of steps is developed and applied to finding proton traps and access points to proton highways in the doped perovskite oxides: AZr_(0.875)D_(0.125)O_3, where A is Ba or Sr and the dopant D is Y or Al. The high centrality region near the dopant is wider in the SrZrO_3 systems than the BaZrO_3 systems. In the aluminum-doped systems, a region of intermediate centrality (secondary region) is found in a plane away from the dopant. Kinetic Monte Carlo (kMC) trajectories show that this secondary region is an entry to fast conduction planes in the aluminum-doped systems in contrast to the highest centrality area near the dopant trap. The yttrium-doped systems do not show this secondary region because the fast conduction routes are in the same plane as the dopant and hence already in the high centrality trapped area. This centrality measure complements kMC by highlighting key areas in trajectories. The limiting activation barriers found via kMC are in very good agreement with experiments and related to the barriers to escape dopant traps.

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© 2015 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License. Received 12 February 2015; accepted 1 April 2015; published online 17 April 2015. We would like to thank Dylan Shepardson for helpful discussions. This research was supported by a NSF RUI Grant No. CHE-1111474 and a Cottrell Science Scholars Multi-investigator award. Computational resources were provided in part by the MERCURY supercomputer consortium http://mars.hamilton.edu under NSF MRI No. CHE-1229354.

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