# Difference between revisions of "Santos-Lopez de Haro-Yuste hard disk equation of state"

$\frac{p}{\rho k_B T} = \left[ 1- b_2 \eta - \frac{(1-b_2 \eta_{\mathrm{max}}) \eta^2}{\eta^2_{\mathrm{max}}} \right]^{-1}$
where $p$ is the pressure, $\rho$ is the number density, $k_B$ is the Boltzmann constant, $T$ is the temperature, $b_2=2$ is the reduced second virial coefficient, $\eta = a_0(\sigma)\rho$ is the packing fraction, with $a_0(\sigma) = (\pi/4)\sigma^2$ the area of a hard disk with diameter $\sigma$, and $\eta_{\mathrm{max}} = \pi \sqrt3 /6$