I recently released a library for calculating charged-particle stopping powers.
As part of the PhD work I ended up writing quite a bit of code to evaluate different stopping models. The problem is that as an energetic charged particle traverses matter, it slows down as it collides with particles in the material. This is pretty well known for room-temperature material, but for plasmas it gets quite complicated and there are many theories that can be used. I developed an object-oriented framework in C++ (with SWIG wrappers for Java and Python) to handle many of the popular theories. Thanks to MIT this is now open source under a GPL license, available at github.