  We apply the recently developed adaptive ensemble optimization technique to
simulate dense Lennard-Jones fluids and a particle-solvent model by
broad-histogram Monte Carlo techniques. Equilibration of the simulated fluid is
improved by sampling an optimized histogram in radial coordinates that shifts
statistical weight towards the entropic barriers between the shells of the
liquid. Interstitial states in the vicinity of these barriers are identified
with unprecedented accuracy by sharp signatures in the quickly converging
histogram and measurements of the local diffusivity. The radial distribution
function and potential of mean force are calculated to high precision.
