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Theory of atomic-scale manipulation in complex molecular systems in STM: Chemistry in the high electrical field

V.S. Gurin*

Belarusian State University

This is an abstract for a talk to be given at the Fifth Foresight Conference on Molecular Nanotechnology.

The author regrets that unexpected events have forced him to cancel his attendance and this presentation.

A number of experimental studies of local modification of solids in STM show a variety of processes responsible for this phenomenon. However, there is no consistent theory that could explain all transformations in solid surface observed in the experiments. The very different chemical nature of materials subjected to STM-stimulated modification and troubles with usage of conventional analytical methods due to small amount of matter in the reactions do not give possibility to elaborate detailed mechanisms (sequence of chemical reactions, transition states, products, etc.). We deal with a theoretical approach to this problem based on quantum-chemical analysis (with ab-initio methods) of the states of a 'nanometer-scale reaction system'. This system consist of a cluster from several atoms and STM tip located at a short distance from it. The high electrical field near the tip has a remarkable effect upon the molecular structure simulated by the finite cluster. The field contributes to the chemical reactivity of molecules and clusters, and some unusual processes may take place and can be used for directed construction on solid surface in nanotechnology.

The approach is applied for some certain systems which are of interest from the experimental point of view (grafite, silver surface, palladium acetate film). Quantum chemical calculations of electronic structure and energetical characteristics of the surface clusters under the STM tip field show pathways of the reconstruction, chemical bond breaking, electronic excitation. Formation of new species being intermediate products of STM-stimulated transformation is proposed.



*Corresponding Address:
Valerij S. Gurin, Physico-Chemical Research Institute, Belarusian State University, Leningradskaja str., 14, 220080, Minsk, BELARUS; fax: 375-172-264696, e-mail: postmaster@phchinst.belpak.minsk.by
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