To calculate to calculate multilayer reflectivities as a function of either the photon energy or incident angle.
The interface is created using the automatic application generator xop_ifc.pro
Scattering factors are precomputed using DABAX "default" f1f2_<name>.dat file
Limitations:
it can only deal with elements (not compounds)
it does not take into account the effect of the roughness at the interfaces.
Users interested in more sophisticated multilayer modeling and fit with experimental data can use the IMD code, available as an XOP extension.