Structural correlations and the “structural diffusion” model for liquids

The local order in liquids is characterized by a set of spatially varying parameters defining a certain local lattice structure at every point in the liquid. The correlations between these parameters at different spatial positions are obtained, in the spirit of the “structural diffusion” model of Prins, from a Fokker-Planck-like equation concerning the spatial change of the probability distribution of the local structure parameters. From the structural correlations qualitatively correct molecular pair distributions are obtained. They depend on chosen lattice constants and “structural” diffusion constants. Possible systematic improvements and refinements of this model are suggested.