Computers simulations applied to study of electrochemically nanostructured systems

E. P. M. LEIVA, S. A. DASSIE, N. LUQUE, P. VÉLEZ, M. MARISCAL, M. ROJAS, O. OVIEDO

Shanghai, China

Simposio; International Symposium on Functional Materials & Interfacial Electrochemistry; 2005

COMPUTERS SIMULATIONS APPLIED TO THE STUDY OFECTROCHEMICALLY NANOSTRUCTURED SYSTEMSE.P.M. Leiva, S.A. Dassie , N. Luque, P. Vélez, M. Mariscal, M.Rojas, O. Oviedo.Unidad de Matemática y Física, Facultad de Ciencias Químicas, Universidad Nacionalde Córdoba, INFIQC, Argentinae-mail: eleiva@fcq.unc.edu.arNanoscale electrochemistry appears as a promising field in which scientists are beginningto generate structures at the atomic and molecular scales in order to obtain surfaces and systemswith novel properties. In the particular case of electrochemistry, nanostructuring on solid surfaceshas been undertaken using different types of techniques, that share a common instrument for theirimplementation - a scanning tunnelling microscope (STM). The exponential dependence of thetunneling current on the tip-surface distance makes this device very sensitive to the topology ofthe surface in the z direction. For this reason, in the origin of the STM techniques, the mostpopular application was to get topological information, but soon an alternative application wasdeveloped, consisting in the possibility of manipulation of matter at the atomic level.Electrochemists have managed to employ the STM in several ways to nanostructure surfaces. Inone of them, denominated tip induced local metal deposition (TILMD), nanoclusters aregenerated on the surface of a substrate by transfer of matter from the tip of the STM. The material on the tip is continuously renewed by deposition from a solution containing ions of the metal to be deposited (1). In a second method defects are generated on a metal surface, and the holes obtained in this way are later decorated through deposition of the foreign metal (2,3). In a third method the tip of an STM was used as an electrochemical nanoelectrode to generatesupersaturation conditions with respect to the bulk metal equilibrium potential, and nucleationand growth of a single clusters is achieved (4,5). A fourth application of the STM consists in thegeneration of nanowires. Moving a STM Au tip into and out of contact with a Au substrate in thepresence of molecules that interact strongly with gold, Xu and Tao (6) were able to generatemonomolecular junctions.While many facts could be explained for the nanostructuring processes mentioned above,an important number of question arose, leaving a fruitful field for theoretical modelling. Althoughstatistical mechanics cannot be applied directly due to the complexity of the problems mentioned,computer simulations provide an alternative way towards the understanding of the atomisticprocesses involved. In those cases where the electronic structure of the system plays an importantrole, quantum mechanical calculations are required. On the other hand, for those system wherethe behavior is the result of the collective interaction of the particles, some approximatedpotential can be employed to describe the interacion between the constituents particles. It thesecases, a more complete statistical description of the system can be made.In the present talk we will discuss on the application of quantum mechanical calculationsand classical simulation methods (molecular dynamics, Monte Carlo) to the problems mentionedabove. Some of the question to be addressed wll be the generation mechanisms of thenanostructures and their stability, in relation to the nature of the materials involved.AcknowledgementThe authors acknowledge financial support from CONICET, Agencia Córdoba Ciencia, SecytU.N.C., Program BID 1201/OC-AR PICT No. 06-12485References1. D.M.Kolb, R. Ullmann, T.Will, Science, 275, 1097 (1997)2. W.Li, G.S. Hsiao, D. Harris, R.M. Nyffenegger, J.A. Virtanen, R.M. Penner, J. Phys. Chem.,100, 20103 (1996).3. X.H. Xia, R. Schuster, V. Kirchner, G. Ertl, J. Electroanal. Chem., 461, 102 (1999).4. W. Schindler, D. Hoffmann, J. Kirschner, J. Appl. Phys. 87, 7007 (2000).5. W. Schindler, P. Hugelmann, M. Hugelmann, F.X. Kärtner, J. Electroanal. Chem., 522, 49(2002).6. B.Xu and N. Tao, Science 301(2003)1123.