Atomic and molecular suspended nanowires, or more properly speaking, nanobridges or nanocontacts, can be fabricated in a number of ways, like mechanically controllable break-junctions, STM break-junctions, metal deposition, electron beam punching or even spontaneous formation of molecular bridges. These contacts, made of atom chains, molecules and probably of both, exhibit a number of amazing properties like quantized conductance, conductance switching, negative differential resistance and quantized breaking force. In the particular case of electrochemistry, besides the potential control of the potential difference between the tip and the substrate, the potential difference between the substrate and a reference electrode can be fixed by means of a bipotentiostat, opening an interesting number of possibilities. Although experimental research in the area is currently growing exponentially, providing clues to answer many of the emergent questions, extensive theoretical research is desirable to provide detailed information on some aspects of the problem that cannot be addressed straightforwardly by experiments. One of these problems is the structure of the nanocontact itself, and the closely related problem of its stability.
In the present work we tackle the latter point by means of density functional calculations and molecular dynamic simulations with semiempirical interaction potentials. In the case of quantum mechanical calculations, they are very useful to provide insight into the electronic structure of the system and give very precise information on the binding of the particles, as well as concerning the forces involved in the generation of the nanocontact. In the case of the classical mechanics calculations, although the energetic information is not exact due to the approximate description of the interaction between the particles, knowledge is gained on the types of configuration that may arise due to the thermal motion of the system. We consider pure metal systems, as well as the intercalation of atomic and molecular species like bipyridine and dithiols.
Acknowledgments: Financial support from CONICET, Agencia Córdoba Ciencia, Secyt UNC, and Program BID 1728/OC-AR PICT No. 06-12485 are gratefully acknowledged,
