Incoherent dynamic structure factors for pure liquid metals and alloys

Investigations of the dynamic structure of liquids by neutron scattering requires to separate coherent from incoherent structure factors. The latter has to be substracted from the measured intensity in order to obtain the former that contains information about collective dynamics. The relevant information lie in the low-q region, where incoherent scattering is important and where the description of the incoherent structure factor has consequently to be accurate. In order to shed light on this methodology, we performed molecular dynamics simulations of pure liquid K and Cs and also of their equiatomic mixture, in which the interactions between atoms are described by pseudopotential formalism. The incoherent dynamic structure factors are calculated and compared with analytical models. It appears that a single Gaussian, as well as a single Lorentzian function are unable to fit accurately the results. Improvements of the fitting function are discussed