Hi Anatoly,
The physics list you have shown me for cross-activation of DNA_Option0 and StandardPhysicsOption4 looks correct. Regarding your error, I believe this is happening because “/process/em/AddDNARegion World DNA_Opt0” needs to be invoked before the run manager is initialized. The run manager can either be initialized in your Geant4 program itself (typically in the main file through runManager->Initialize()) or in the macro through /run/initialize. You may have to comment out the line of code in your Geant4 program and instead call it in your macro. With a macro looking like:
/run/verbose 1
/event/verbose 0
/tracking/verbose
/process/em/AddDNARegion World DNA_Opt0
/run/initialize
/gun/particle gamma
/gun/energy 1.25 MeV
/run/beamOn 500000000
What you have said is correct only DNA_PhysicsOption0 can be registered with a standard physics model at the same time. You can not currently use Option2 in addition to other physics models.
All of the volumes located in world will be calculated with Option0 physics and when DNA physics are not applicable (usually when your particle has an energy greater than 1 MeV) the StandardPhysics_Option4 will be used.
Option0 refers to the initial version of Geant4DNA. Any publications prior to when the additional Geant4 DNA options became available will describe this physics model thoroughly.
Hope this is helpful,
Joseph