Dependence on the thermodynamic state of self-diffusion of pseudo-hard-sphere and Lennard-Jones potentials

Self-diffusion D in a system of particles that interact with a pseudo-hard-sphere or a Lennard-Jones potential is analyzed. Coupling with a solvent is represented by a Langevin thermostat, characterized by the damping time t_{d}. The hypotheses that D=D_{0}φ is proposed, where D_{0} is the small concentration diffusivity and φ is a thermodynamic function that represents the effects of interactions as concentration is increased. Molecular dynamics simulations show that different values of the noise intensity modify D_{0}, but do not have an effect on φ. This result is consistent with the assumption that φ is a thermodynamic function since the thermodynamic state is not altered by the presence of damping and noise.