Even if our PP looks good (or not too bad) on paper based on the results of atomic calculations, it is always a good idea to test it in simple molecular or solid-state systems, for which all-electron data (i.e. calculations performed with the same XC functional but without PP's, such as e.g. FLAPW, LMTO, Quantum Chemstry calculations) is available. The comparison with experiments is of course interesting, but the goal of PP's is to reproduce AE data, not to improve DFT.