Ar or He diffusion in crystal is often approximated to 1D diffusion (diffusion out of a sphere, infinite cylinder or infinite slab) for simple analytical treatment. Recent studies have shown that for small anisotropy (shape and/or diffusion coefficients) diffusive flux of Ar/He out of crystal can be successfully approximated by a sphere with an equivalent Surface to Volume ratio provided the anistropy is small. In this work we derive a new analytical model to offers a better correction for a much greater range of anisotropy. We call this model Average Normalized Distance (AND). The manuscript was published in GCA (Huber, C., Cassata, W., and Renne, P.; 2011).
Additionally, I developed a new numerical model for diffusion that can deal with arbitrarily complex boundary topology with no additional cost in terms of algorithm. A separate paper for this model was published in the International Journal of Modern Physics C (Huber, C, Dufek, J., and Chopard, B., 2011). This code allows users to basically scan thin section and solve for diffusion into/out of crystals. Here is an example of the method with Buzz the mascot of GTech