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We rigorously establish a physical time scale for a general class of kinetic Monte Carlo algorithms for the simulation of continuous-time Markov chains. This class of algorithms encompasses rejection-free (or BKL) and rejection (or "standard") algorithms. For rejection algorithms, it was formerly considered that the availability of a physical time scale (instead of Monte Carlo steps) was empirical, at best. Use of Monte Carlo steps as a time unit now becomes completely unnecessary.

We develop a phenomenological model of electro-mechanical ferroelectric fatigue\ud based on a ferroelectric cohesive law that couples mechanical displacement and\ud electric-potential discontinuity to mechanical tractions and surface-charge density.\ud The ferroelectric cohesive law exhibits a monotonic envelope and loading-unloading\ud hysteresis. The model is applicable whenever the changes in properties leading to\ud fatigue are localized in one or more planar-like regions, modelled by the cohesive\ud surfaces. We validate the model against experimental data for a simple test configuration consisting of an infinite slab acted upon by an oscillatory voltage differential across the slab and otherwise stress free. The model captures salient features of the experimental record including: the existence of a threshold nominal field for the onset of fatigue; the dependence of the threshold on the applied-field frequency; the dependence of fatigue life on the amplitude of the nominal field; and the dependence of the coercive field on the size of the component, or size effect. Our results, although not conclusive, indicate that planar-like regions affected by cycling may lead to the observed fatigue in tetragonal PZT.Peer ReviewedPostprint (author's final draft

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