  Recent efforts for the improvement of the accuracy of physics data libraries
used in particle transport are summarized. Results are reported about a large
scale validation analysis of atomic parameters used by major Monte Carlo
systems (Geant4, EGS, MCNP, Penelope etc.); their contribution to the accuracy
of simulation observables is documented. The results of this study motivated
the development of a new atomic data management software package, which
optimizes the provision of state-of-the-art atomic parameters to physics
models. The effect of atomic parameters on the simulation of radioactive decay
is illustrated. Ideas and methods to deal with physics models applicable to
different energy ranges in the production of data libraries, rather than at
runtime, are discussed.
