Dear all.
I have a couple of questions about dispersion coefficients.
The TOPAS user manual states:
TOPAS 4-2 Technical Reference, page 33 wrote
Dispersion coefficients (f[sub]a[/sub]' and f[sub]a[/sub]") used are found in the SSF directory.
...
Dispersion coefficients and mass attenuation coefficients for Z > 92 have been calculated using the FPrime software (Larson & Von Dreele, 2004), covering the energy range from 4 to 77 keV.
Looking up Np is the SSF directory at approximateley 35 keV, I read;
[m]
E(eV) f1 f2
34933 91.66 5.415[/m]
However, when I use the Fprime program (available
here), I get the following figures.
[m]Element= Np f'=-1.340 f"= 5.415[/m]
How are the two f' values related?
Secondly, (maybe a naive question), how do I inut the values of f' and f'' into my inp file, or is it automatic? I am used to having to enter values manually in GSAS.
Many thanks
Adrian