When Si = 0, the Ei term goes to infinity. QFim is set to zero in this case.
To avoid issues with numerical instability when the result of exp becomes very large, when (Si/aim > 100), we round QFim down to zero.
With certain combinations of inputs, it is possible for the QFim
equation above to evaluate to a small negative number. In these cases is rounded to zero.
You can look at the equations in the quickflow section of the User Guide and review your inputs, as well as the output file intermediate_outputs/Si.tif to see if anything explains the 0 result. Let us know what you find.