Lower limit on geometry dimensions?

Geometry, Fields and Transportation
1

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

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2

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.