Figure 3.

Schematic representation of the CFCMC algorithm. (a) System close to saturation (the host structure is represented in gray, and the adsorbed molecules are in blue). (b) Close to saturation, most attempts to insert a new molecule in a single step (dashed red circles) will result in an overlap with other molecules or with the host structure. (c) In CFCMC, insertions are facilitated by using a molecule with scaled interactions (a fractional molecule). Attempts to insert a fractional molecule have a higher probability of being accepted because the energy penalty due to overlaps is smaller. Once the fractional molecule is inserted, the surrounding molecules rearrange (black arrows) to minimize the repulsive interactions in the system. (d) For the fractional molecule to become a integer molecule, enough space has to be created. The configuration with N + 1 adsorbed molecules (dark blue) can be very different from the configuration with N adsorbed molecules (light blue). Close to saturation, inserting a molecule requires the collective motion of surrounding molecules.