Structure and dynamics of a supercritical fluid in comparison with a liquid

The static and dynamic structure of a liquid and a supercritical fluid are investigated by molecular dynamics calculations. The states have been selected so as to generate pair correlation functions which have the same height for the first peak. The resulting pressure of the fluid was about 10 kbar, whereas that of the liquid was only a few bar. Marked differences have been found in detail for both the static and the dynamic properties of the system at these states. In particular, the form of the dynamic correlation functions is appreciably altered for the fluid compared with the liquid. The following quantities have been calculated: internal energy, pressure, the diffusion coefficient, static pair and triplet correlation functions, the mean-square displacement, velocity autocorrelation function and its Fourier transform, and the dynamic pair correlation functions.