  During the last few years, a number of works in computer simulation have
focused on the clustering and percolation properties of simple fluids based in
an energetic connectivity criterion proposed long ago by T.L. Hill [J. Chem.
Phys. 23, 617 (1955)]. This connectivity criterion appears to be the most
appropriate in the study of gas-liquid phase transition. So far, integral
equation theories have relayed on a velocity-averaged version of this
criterion. We show, by using molecular dynamics simulations, that this average
strongly overestimates percolation densities in the Lennard-Jones fluid making
unreliable any prediction based on it. Additionally, we use a recently
developed integral equation theory [Phys. Rev. E 61, R6067 (2000)] to show how
this velocity-average can be overcome.
