In RASPA, it is assumed that the gas phase is ideal; hence, the departure function is always set to zero. This is true for low-pressure values and high temperatures. However, at room temperature and high pressures, this term becomes important. One can calculate the departure function using the (experimental) equation of state. In this work, we suggest an alternative approach. At a given pressure, an NPT (constant number of particles, pressure, and temperature) Monte Carlo simulation at 25 • C is performed to compute the density of the system (ρ), and the energy per mol of the adsorbate of interest ( U N ). The enthalpy per mol of the adsorbate of interest ( H N ) is obtained using the first law of thermodynamics: