As a corrallary to #182 It would be nice to be able to pass fixed values to the model without making them fit parameters that the user would need to not check. For example, temperature and dielectric constants in the Hayter Penfold MSA structure factor are physical constants that cannot be defined in the model since one does not know a priori which temperature the experiment is carried out at or in what solvent (which will affect the dielectric constant). In re-parameterized models, things like volumes or densities of moieties may be needed and are tabulated but often as a function of temperature which again would be unknown a priori when writing the model.
This is less urgent however than #182 since the model can still be written by pretending these values could be fittable whereas derived values have to be hand computed by the users.
As a corrallary to #182 It would be nice to be able to pass fixed values to the model without making them fit parameters that the user would need to not check. For example, temperature and dielectric constants in the Hayter Penfold MSA structure factor are physical constants that cannot be defined in the model since one does not know a priori which temperature the experiment is carried out at or in what solvent (which will affect the dielectric constant). In re-parameterized models, things like volumes or densities of moieties may be needed and are tabulated but often as a function of temperature which again would be unknown a priori when writing the model.
This is less urgent however than #182 since the model can still be written by pretending these values could be fittable whereas derived values have to be hand computed by the users.