Molecular dynamics simulation and nonlinear analysis of density fluctuations in Lennard-Jones fluid system near the critical point

•The spatiotemporal density variation of argon near the critical point is studied.•The deviations display M-shape distribution with increases of average densities.•Evolution of three regimes (liquid-like, two-phase-like and gas-like) are observed.•The time series of local densities behave either chaotic or random characteristics.