How is RadL determined in mixtures?

I was checking the penetration depth of alpha’s and Li7 ions in my material and found something strange. The material is a mixture of Boron Nitride (RadL 20.592cm) and G4_POLYSTYRENE (RadL 41.313cm). Now my Mixture0 with a 1BN:1Polystyrene ratio has a RadL of 30.871 while Mixture1 with a ratio of 2BN:1Polystyrene has a RadL of 34.189. Isn’t it strange that the RadL increases when there is more of the low RadL component in the material? Is there a physical reason for this or is there something wrong in my code?

Below the output of my materialstable:


Material: MatrixMaterial 0 density: 1.407 g/cm3 RadL: 30.871 cm Nucl.Int.Length: 55.599 cm
Imean: 74.329 eV temperature: 293.15 K pressure: 1.00 atm

—> Element: B (B) Z = 5.0 N = 11 A = 10.811 g/mole
—> Isotope: B10 Z = 5 N = 10 A = 10.01 g/mole abundance: 19.900 %
—> Isotope: B11 Z = 5 N = 11 A = 11.01 g/mole abundance: 80.100 %
ElmMassFraction: 29.04 % ElmAbundance 25.60 %

—> Element: N (N) Z = 7.0 N = 14 A = 14.007 g/mole
—> Isotope: N14 Z = 7 N = 14 A = 14.00 g/mole abundance: 99.632 %
—> Isotope: N15 Z = 7 N = 15 A = 15.00 g/mole abundance: 0.368 %
ElmMassFraction: 37.63 % ElmAbundance 25.60 %

—> Element: C © Z = 6.0 N = 12 A = 12.011 g/mole
—> Isotope: C12 Z = 6 N = 12 A = 12.00 g/mole abundance: 98.930 %
—> Isotope: C13 Z = 6 N = 13 A = 13.00 g/mole abundance: 1.070 %
ElmMassFraction: 30.75 % ElmAbundance 24.40 %

—> Element: H (H) Z = 1.0 N = 1 A = 1.008 g/mole
—> Isotope: H1 Z = 1 N = 1 A = 1.01 g/mole abundance: 99.989 %
—> Isotope: H2 Z = 1 N = 2 A = 2.01 g/mole abundance: 0.011 %
ElmMassFraction: 2.58 % ElmAbundance 24.40 %


Material: MatrixMaterial 1 density: 1.268 g/cm3 RadL: 34.189 cm Nucl.Int.Length: 62.595 cm
Imean: 76.290 eV temperature: 293.15 K pressure: 1.00 atm

—> Element: B (B) Z = 5.0 N = 11 A = 10.811 g/mole
—> Isotope: B10 Z = 5 N = 10 A = 10.01 g/mole abundance: 19.900 %
—> Isotope: B11 Z = 5 N = 11 A = 11.01 g/mole abundance: 80.100 %
ElmMassFraction: 34.85 % ElmAbundance 33.86 %

—> Element: N (N) Z = 7.0 N = 14 A = 14.007 g/mole
—> Isotope: N14 Z = 7 N = 14 A = 14.00 g/mole abundance: 99.632 %
—> Isotope: N15 Z = 7 N = 15 A = 15.00 g/mole abundance: 0.368 %
ElmMassFraction: 45.15 % ElmAbundance 33.86 %

—> Element: C © Z = 6.0 N = 12 A = 12.011 g/mole
—> Isotope: C12 Z = 6 N = 12 A = 12.00 g/mole abundance: 98.930 %
—> Isotope: C13 Z = 6 N = 13 A = 13.00 g/mole abundance: 1.070 %
ElmMassFraction: 18.45 % ElmAbundance 16.14 %

—> Element: H (H) Z = 1.0 N = 1 A = 1.008 g/mole
—> Isotope: H1 Z = 1 N = 1 A = 1.01 g/mole abundance: 99.989 %
—> Isotope: H2 Z = 1 N = 2 A = 2.01 g/mole abundance: 0.011 %
ElmMassFraction: 1.55 % ElmAbundance 16.14 %


Material: BN density: 2.100 g/cm3 RadL: 20.592 cm Nucl.Int.Length: 38.657 cm
Imean: 79.444 eV temperature: 293.15 K pressure: 1.00 atm

—> Element: B (B) Z = 5.0 N = 11 A = 10.811 g/mole
—> Isotope: B10 Z = 5 N = 10 A = 10.01 g/mole abundance: 19.900 %
—> Isotope: B11 Z = 5 N = 11 A = 11.01 g/mole abundance: 80.100 %
ElmMassFraction: 43.56 % ElmAbundance 50.00 %

—> Element: N (N) Z = 7.0 N = 14 A = 14.007 g/mole
—> Isotope: N14 Z = 7 N = 14 A = 14.00 g/mole abundance: 99.632 %
—> Isotope: N15 Z = 7 N = 15 A = 15.00 g/mole abundance: 0.368 %
ElmMassFraction: 56.44 % ElmAbundance 50.00 %


Material: G4_POLYSTYRENE density: 1.060 g/cm3 RadL: 41.313 cm Nucl.Int.Length: 68.750 cm
Imean: 68.700 eV temperature: 293.15 K pressure: 1.00 atm

—> Element: C © Z = 6.0 N = 12 A = 12.011 g/mole
—> Isotope: C12 Z = 6 N = 12 A = 12.00 g/mole abundance: 98.930 %
—> Isotope: C13 Z = 6 N = 13 A = 13.00 g/mole abundance: 1.070 %
ElmMassFraction: 92.26 % ElmAbundance 50.00 %

—> Element: H (H) Z = 1.0 N = 1 A = 1.008 g/mole
—> Isotope: H1 Z = 1 N = 1 A = 1.01 g/mole abundance: 99.989 %
—> Isotope: H2 Z = 1 N = 2 A = 2.01 g/mole abundance: 0.011 %
ElmMassFraction: 7.74 % ElmAbundance 50.00 %

When you build MatrixMaterial from BN and polystyrene, these 2 materials must be added by weight (eg massFraction).
Examples can be found in TestEm0 (ArgonButane) and TestEm3 (Aerogel).

That is what I did but I made a mistake in my previous post. Matrixmaterial0 has a massratio of 2:1 (BN:Polystyrene) and Matrixmaterial1 has a 4:1 massratio.

My question about the radL still stands:
Mixture0: low amount BN (with low RadL) --> RadL = 30.871
Mixture1: higher amount of BN --> should lower the RadL but… --> RadL = 34.189

Same goes for Nucl.Int.Length.

Am I missing something? Maybe something with the density?

I found the problem! There was something wrong in my calculation of the density which caused the problem. Finally… I’ve been looking for this over a month.