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Forum: Geometry
Re: None Re: What is the correct way to create a G4Element consisting of a single G4Isotope? (Michael H. Kelsey)
Date: 30 Oct, 2018
From: Sergio Losilla <Sergio Losilla>

Hi again,

> G4Element, on the other hand, is designed to be some combination of
> isotopes, and is build around "chemical" definitions and assumptions.  In
> particular, in a mixture of isotopes, the effective "number of nucleons" is
> taken as just the molar mass divided by N_A, which is a double.
> You can see in G4Element.hh that GetAtomicMassAmu() and GetN() return the
> same value, A/(g/mol).  The latter is just shorthand for the former.

Hmmm, OK, looking at G4Element.hh in more detail answered my question:

    134:  // Atomic weight in atomic units
    135:  inline G4double GetN()             const {return fNeff;}
    136:  inline G4double GetAtomicMassAmu() const {return fNeff;}

So G4Element::GetN() returns the atomic weight, and not the average N.

Is this standard notation? I apologize if this is a silly question, I am not a particle or nuclear physicist but a computational physics outsider...

I mean, at the moment it seems that:

   A_element = sum_isotope w_isotope * A_isotope
   N_element = A_element/(g/mol)

instead of what I expected

   A_element = sum_isotope w_isotope * A_isotope
   N_element = sum_isotope w_isotope * N_isotope

My main worry is that I am defining the element wrong, and that a wrong value of N is used at some stage of the simulation yielding wrong results. But I guess I can proceed safely.

Cheers,

Sergio

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