We are concerned with a model of ionic polymer-metal composite (IPMC) materials that consists of a coupled system of the Poisson and Nernst-Planck equations, discretized by means of the finite element method (FEM). We show that due to the transient character of the problem it is efficient to use adaptive algorithms that are capable of changing the mesh dynamically in time. We also show that due to large qualitative and quantitative differences between the two solution components, it is efficient to approximate them on different meshes using a novel adaptive multimesh hp-FEM. The study is accompanied with numerous computations and comparisons of the adaptive multimesh hp-FEM with several other adaptive FEM algorithms.

We describe a newly-developed defect generation mechanism, namely the grain boundary Frenkel pair (GBFP) model, and corresponding diffusion mechanisms during electromigration developed using atomic molecular statics (MS), Monte Carlo (MC), and molecular dynamics (MD) simulation techniques in Al and Al-Cu. We contend that large numbers of interstitials and vacancies exist at grain boundaries and both contribute to mass transport. Cu preferentially segregates to the interstitial sites at grain boundaries via a Frenkel pair generation process and reduces the overall grain boundary diffusivity due to the strong binding in the Al-Cu dimer. Predictions from our models are in excellent agreement with available experimental data and observations.