The Widom line in two- and three-dimensional fluids: Similarities and differences.

We compute the properties of four systems across a broad range of thermodynamic parameters, traversing the Widom delta region. This allows us to trace the structural evolution of a supercritical fluid as its density increases from gas-like to liquid-like values. For the first time, we determine the Widom line for a two-dimensional Lennard-Jones fluid and compare it with its three-dimensional counterpart. Furthermore, we analyze the probability distribution of Voronoi cell volumes and contrast the Voronoi volume of individual particles with the system's average volume. Finally, we identify universal properties in the behavior of supercritical fluids for the Lennard-Jones system, methanol, and water.