Material sorting influence in Energy Cuts

Dear experts,

Few months ago, when starting to use Geant4, I asked the forum wether the order in defing compounds in a material
would affect the simulation results. The logical answer was that this effect
vanishes for a large amount of events, leading to statistical equivalent results.

Several courses and simulations to get my code functioning with large enough gunned particles
for the statistics, I am struggling with computational time. I was suggested to define energy cuts
for the neutrons in my simulations, which seems to work properly but the same problem arises now:
When reordering the material compounds the simulation takes much longer and also seem to
invalidate these cuts (in this case when placing hydrogen -water- first when creating the material). I also get
rather different results -greater than what I get with different random seeds- when using the following soils:

G4Material* Soil1 = new G4Material(name="Soil1", 1.7*g/cm3, ncomponents=11);
Soil1->AddMaterial(Na2O, fractionmass= 0.02373);
Soil1->AddMaterial(MgO, fractionmass= 0.06156);
Soil1->AddMaterial(Al2O3, fractionmass= 0.09221);
Soil1->AddMaterial(SiO2, fractionmass= 0.52715);
Soil1->AddMaterial(SO3, fractionmass= 0.04092);
Soil1->AddElement(elCl, fractionmass= 0.00563);
Soil1->AddMaterial(K2O, fractionmass= 0.00464);
Soil1->AddMaterial(CaO, fractionmass= 0.0653);
Soil1->AddMaterial(TiO2, fractionmass= 0.01028);
Soil1->AddMaterial(FeO, fractionmass= 0.14858);
Soil1->AddMaterial(H2O, fractionmass= 0.02);

G4Material* Soil2 = new G4Material(name="Soil2", 1.7*g/cm3, ncomponents=11);
Soil2->AddMaterial(H2O, fractionmass= 0.02);
Soil2->AddMaterial(Na2O, fractionmass= 0.02373);
Soil2->AddMaterial(MgO, fractionmass= 0.06156);
Soil2->AddMaterial(Al2O3, fractionmass= 0.09221);
Soil2->AddMaterial(SiO2, fractionmass= 0.52715);
Soil2->AddMaterial(SO3, fractionmass= 0.04092);
Soil2->AddElement(elCl, fractionmass= 0.00563);
Soil2->AddMaterial(K2O, fractionmass= 0.00464);
Soil2->AddMaterial(CaO, fractionmass= 0.0653);
Soil2->AddMaterial(TiO2, fractionmass= 0.01028);
Soil2->AddMaterial(FeO, fractionmass= 0.14858);

The Figure I’m showing reflects the squared differences against a real observation of the process I am trying to study.
I don’t know why this happen, rather than thinking on a non homogeneous material “soil” is built.

Thank you in advance.


1 Like