How to define the heavy water (D2O)

No code provided, I am the beginnger

Start with and Material — Book For Application Developers 10.7 documentation

You may also want to look at the Geant4 basic examples which are included with the distribution.

examples/extended/hadronic/Hadr06/src/ : lines 98-105

Dear maire,
thank you, I will do this .

Dear mkelsey,
thank you, This helped me a lot .