Peculiarities in the Simulation of Optical Physics with Geant4

Geant4 is a complex and widely-used software toolkit for the simulation of the passage of particles through matter and the interactions they undergo. It contains very extensive and flexible optical physics capabilities. These allow for the specification of a lot of properties for materials and surfaces as well as for the optical physics process itself. Because of this large variety of possible adjustments, there is a number of peculiarities of the optical physics in Geant4, which the user has to be aware of in order to avoid incorrect simulation results due to user mistakes. As these peculiarities are not always easy to recognise, this can be a serious problem, especially for less experienced users of Geant4. In order to assist users of optical physics in Geant4 in avoiding mistakes, this paper gives a summary of peculiarities of the optical physics in Geant4.