Dear Sir,

I tried to simulate optical photons and I tried to define scintillator properties. I found that GEANT4 makes incorrect interpolation when I try to define more than 2 data points on energy grid.... The origin of the problem is in "G4PhysicsOrderedFreeVector.cc" file.

In "G4PhysicsOrderedFreeVector.cc" there is the function to get an energy value:

G4double G4PhysicsOrderedFreeVector::GetEnergy(G4double aValue)
{
        G4double e;
        if (aValue <= GetMinValue()) {
          e = edgeMin;
        } else if (aValue >= GetMaxValue()) {
          e = edgeMax;
        } else { 
          size_t closestBin = FindValueBinLocation(aValue);
          e = LinearInterpolationOfEnergy(aValue, closestBin);
	}
        return e;
}
But instead of:

inline
G4double G4PhysicsOrderedFreeVector::GetMaxLowEdgeEnergy()
{
	return binVector.back();
}
inline
G4double G4PhysicsOrderedFreeVector::GetMinLowEdgeEnergy()
{
	return binVector.front();
}
"GetMinValue()" and "GetMaxValue()" are used !!!!

Additionaly,  "e = LinearInterpolationOfEnergy(aValue, closestBin)" looks very strange because inside of "LinearInterpolationOfEnergy"  you make interpolation of the function values (dataVector[]) instead of energy grid (binVector[]).

Please check it!