Hi Daniel I'm currently simulating the optical phenomena of the LYSOCe (in my case) and it's properties wasn't recognized by GATE, so this was solved when I copied the GateMaterials.db, Materials.xml and Surfaces.xml to my $HOME directory, also in the GATEHOME and the directory in which there is the mac files. Hope this helps, I'm interesting in the H8500 simulation too Best regards -- e- + e+ -> <~~*~~>