Top: different cluster radius definitions. Blue line: radius based on the maximal inter-atomic distance from DFT (density functional theory) simulations (Berardo et al. 2014). Orange line: Radius based on the ConvexHull volume approximation of cluster geometry from Berardo et al. (2014) with added Van der Waals interaction distance. Green line: (Eq. (5)). Purple line: radius based on volume of smallest box containing cluster with added Van der Walls interaction distance. Bottom: Cluster number densities from MC code using different radius definitions. Solid lines: (Eq. (5)); dotted lines: box approximation/van-der-Waals radius (purple line in upper panel).