Photoelectric model parameterization data optimized - livermore/epics2014

Parameterisation dataset for photoelectric effect model. Original cross-section data are taken from the EPICS (Electron Photon Interaction Cross Sections) v.2014 data bank. The parameterisation is done in two phases with two different energy ranges (delimited by a low and high threshold). Thresholds are dynamically set and depend on the ionisation energy of the element.