The basic structural &magnetic properties of rare earth ions and metals are discussed.A theory of the electronic structure of rare earth ions is introduced using Self Interaction Corrected Relativistic Spin polarised Density FUnctional Theory (SIC-R-SP-DFT). The ~rystal environment is modelled using the Linear Muffin Tin Orbital (LMTO) method. X-ray scattering from a single electron is discussed using covariant perturbation theory and is then elaborated on for the SIC-R-SP-LMTO environment. The details of the xray scattering calcul~tions are considered. Results for x-ray scattering from the heavy rare earths from Gadolinium to Thulium are compared to experiment. It is found that the asymmetry ratio determined in an ab-initio fashion using the aforementioned elements compares favourably with experimental data. The secondary feature of the asymmetry ratio for a particular geometry is found to be dipolar in nature.