In file /geant4.10.07/source/materials/src/G4DensityEffectData.cc, lines 274-277: name of material with index 37 should be "G4_Rb" (Rubidium, Z=37), not "G4_Ru" (Ruthenium, Z=44)
Hello, thank you very much for this report. The fix is committed to the master and will be available with the next patch to 10.7 and in the next public version of Geant4. VI