In practice, V C is approximated as the volume of fused spheres with the Van-der-Waals radii of the respective atoms and varied by scaling the Van-der-Waals radii. The procedure is illustrated in Fig. and forms the basis of the eXtreme Pressure Polarizable Continuum Model (XP-PCM) framework, which has continuously been evolved over the past fifteen years. Recently, the pressure-modified PES G t (P, R) has been calculated as the Legendre transform of G el-rep , G