Molecular dynamics of hard parallel s$\stackrel{\mathrm{´}}{\mathrm{q}}$uares subject to periodic boundary conditions appear to lead to a first-order phase transition with a van der Waals loop (at least for a system of 400 particles). The density change across the transition is small (about 2%). Results on the self-diffusion and velocity autocorrelation function $\rho \mathrm{}\left(t\right)\mathrm{}$ for 400 and 900 particles are also presented. $\rho \mathrm{}\left(t\right)\mathrm{}$ decays exponentially for short times, and at least in the intermediate fluid density, decays at $t^{-1\mathrm{}}$ for long times $t$. In the solidlike region anticorrelating effects predominate.

• Received 29 February 1972

DOI:https://doi.org/10.1103/PhysRevA.6.1153