A Composite Ansatz for Calculation of Dynamical Structure Factor

We propose an ansatz without adjustable parameters for the calculation of a dynamical structure factor. The ansatz combines the quasi-particle Green's function, especially the contribution from the renormalization factor, and the exchange-correlation kernel from time-dependent density functional theory together, verified for typical metals and semiconductors from a plasmon excitation regime to the Compton scattering regime. It has the capability to reconcile both small-angle and large-angle inelastic x-ray scattering (IXS) signals with much-improved accuracy, which can be used as the theoretical base model, in inversely inferring electronic structures of condensed matter from IXS experimental signals directly. It may also be used to diagnose thermal parameters, such as temperature and density, of dense plasmas in x-ray Thomson scattering experiments.