If you look at the post thread [I can not simulated C12(n,α)Be9 reaction you will see that the 12C(n,alpha) 9Be reaction is represented in the Geant4 data base. The (n,3alpha), however, is absent. That was with Geant4 version 11.0.2
If you look at the post thread [I can not simulated C12(n,α)Be9 reaction you will see that the 12C(n,alpha) 9Be reaction is represented in the Geant4 data base. The (n,3alpha), however, is absent. That was with Geant4 version 11.0.2