Lower limit on geometry dimensions?

Geant4 Version: v11.2.1

Hello all,

I want to investigate the energy loss of low energy charged particles in nanoparticles of various sizes and materials. My code compiles and runs regardless of the dimensions I use. However, I’m assuming that there is a practical limit to the size of my geometry, below which results become unreliable. Is there an approximate threshold for this? What sources of error would be introduced if I made each particle 1 nm diameter and set /process/eLoss/StepFunction 0.05 0.1nm?

Due to the restriction of the DNA physics lists to gold and water, I’m using G4Livermore with an electron energy threshold of 10eV.

Thanks!
Aaron

An obvious threshold will be the geometry tolerance (see G4GeomertyTolerance.hh), which is deteremined as a fraction 1e-11 of the world volume. This gets used, for example, in deciding whether a given position is inside, outside, or on the surface of a volume.

If you place your nanoparticles in a 1 m world volume, you’re going to have problems. If you make your world volume 1 um, then the tolerance will be shrunk appropriately.

Other things like production cuts or range cuts will also need to be adjusted to match your tiny volumes.