Neutron magnetic form factor in strongly correlated materials

We introduce a formalism to compute the neutron magnetic form factor F(q) within a first-principles Density Functional Theory (DFT) + Dynamical Mean Field Theory (DMFT). We use our method to compute the form factor of PuCoGa5. We find that the local physics of this material is described by a mixed valence mechanism of the type observed in elemental Plutonium. This picture explains nicely the experimental neutron form factor of PuCoGa5 and it is consistent with the photo-emission spectra shape and the value of the specific heat linear coefficient.