Methodology:
Geometry optimization and normal mode frequency calculation of CHD monomer along with all the studied (CHD)n(n = 2-6) clusters were performed employing B3LYP functional in conjunction with 6-311++g** basis set. For calculation of binding energies of the clusters, basis set superposition errors (BSSE) were corrected using the single point counterpoise method of Boys and Bernardi59. Further, counterpoise corrected single point energies for all the species were calculated at M06-2X/6-311++g** level using the geometries optimized at B3LYP/6-311++g** level. The total binding energy of a cluster comprising of n monomeric CHDs is defined by equation. (1)