  We derive ab initio optical potentials from self-consistent Green's function
(SCGF) theory and compute the elastic scattering of neutrons off oxygen and
calcium isotopes. The comparison with scattering data is satisfactory at low
scattering energies. The method is benchmarked against no-core shell model with
continuum (NCSMC) calculations, showing that virtual excitations of the target
are crucial to predict proper fragmentation and absorption at higher energies.
This is a significant step toward deriving optical potentials for medium mass
nuclei and complex many-body systems in general.
