  We present several equilibrium methods that allow to compute isentropic
processes, either during the compression or the release of the material. These
methods are applied to compute the isentropic release of a shocked monoatomic
liquid at high pressure and temperature. Moreover, equilibrium results of
isentropic release are compared to the direct nonequilibrium simulation of the
same process. We show that due to the viscosity of the liquid but also to
nonequilibrium effects, the release of the system is not strictly isentropic.
