Property surfaces, intermolecular interaction electronic structures

Exemplary manifestations of the existence of intermolecular interactions [1] are the capillary rise of liquids in glass tubes and surface tension phenomena, already investigated in the 19 century, and explained in terms of mutual attraction between molecules in the liquid state. However, the first consistent identification of their attractive nature was achieved by van der Waals, in his study of real gases, but the origin and properties of the intermolecular interactions were only properly understood when the development of Quantum Mechanics allowed a full understanding of the electronic structure of atoms and molecules, and of their interaction. 

Quantum-chemical ab initio calculations have become an alternative to experiments for determining accurately structures, vibrational frequencies and electronic properties as well as intermolecular forces and molecular reactivity.28-31 Two specific approximations were developed to solve the problems of surface chemistry periodic approximation, where quantum-chemical method employs a periodic structure of the calculated system and cluster approximation, where a model of solid phase of finite size is created as a cutoff from the system of solid phase (it produces unsaturated dangling bonds at the border of the cluster). Cluster approximation has been widely used for studying interactions of molecules with all types of solids and their surfaces.32 This approach is powerful in calculating the systems with deviations from the ideal periodic structure like doping and defects. 

This approach combines two appealing features, namely, cohesion of extended ID assemblies on the surface as a result of intermolecular tt-stacking of the porphyrins and the formation of these structures on an insulating surface. The cohesion guarantees an electronic interaction along the axis of the wires and the use of an insulating surface is a prerequisite to further characterize the elecflonic properties of the objects. 

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