Model for self-assembly of Br–H and Br–Br bonded Br4Py molecules

A model, based on the pairwise intermolecular halogen–hydrogen (Br–H) and halogen–halogen (Br–Br) bonding, is proposed to describe the self-assembly of Br4Py molecules into two different planar structures (Phase I and Phase II). The pair bonding interactions are calculated by the density functional theory for the two-molecule and four-molecule clusters. It is shown that about 60% of bonding strength is due to the electrostatic Br(top)–Br(belt) interactions, while the remaining originates from Br–H interactions. The obtained values of pair interactions are further used for Monte Carlo calculations. The model for these calculations is proposed on a square lattice. The two main pair interactions are needed for the emergence of the Phase I ordering, while the Phase II ordering is obtained using a single interaction. The obtained results explain the emergence of both phases.