Single particle dynamics in liquid systems

The subject of this PhD work is the microscopic dynamics in fluids, that is, a study of the behavior of these fluids at an atomic level, where the ps and nm time and length scales, respectively, are involved. The objects of the analysis are fundamental space/time autocorrelation functions of microscopic variables describing either collective or single-particle (self) properties of the system. In particular, in this thesis we exploited molecular dynamics simulation data-sets to describe the self dynamics of fluids belonging to different categories: Lennard-Jones (LJ) model fluids, semi-quantum fluids, liquid metals and hydrogen-bonded molecular liquids. A substantial step forward in the comprehension of single-particle dynamics has been possible i) by applying a new method, not attempted so far, for the description of self functions, which is based on the recently presented multi-exponential expansion theory that accounts for time autocorrelation functions in many-body Hamiltonian systems, and ii) by deepening the relationship between self and collective properties.