CLUSTERS DEPOSITION ON SURFACE AN ATOMIC SCALE STUDY BY COMPUTER SIMULATION METHOD

A nanoparticle contains from a few atoms for the smallest ones to several thousand for the largest ones considered here. The properties of an atom result from quantization and the same is true for the molecules they form. The same is thus true for the smallest nanoparticles. At the other edge, many of the properties of macroscopic materials are well described by a classical approach and nanoparticles appear as objects at the fringing field between quantum and classical behaviors. In the study of their properties, using either a quantum or a classical approach, atomic scale methods appear as naturally well-suited. Atoms are considered as individual objects interacting via their outer shell electrons only. However even with such an approximation, solving the Schrödinger equation becomes quickly prohibitively heavy as the number of atoms involved increases. For the heaviest elements, relativistic effects make the problem even heavier. In this case, the classical approach is the only one presently practical. Ab initio calculation is frequently used to predict small particles configurations as well as their electronic and magnetic properties. In principle, the method is exact. Uncertainties about the origin of correlation exchange however, and also the complexity of setting up efficient numerical algorithms suggest the need of experimental confirmation in many cases. The classical approach to atomic interactions makes use of semi-empirical models fitted on atomic collision properties at high energy (of the order of core electron binding energies or higher) and on solid state properties at low energies (of the order of cohesive energies or lower). Interaction between atoms in a nanoparticle and the interaction of nanoparticles with surfaces presented in this report belong to the latter category. For these, interaction potentials are set up as functionals of the local electron density or of hopping integrals and parameterized on the basis of a range of microscopic and macroscopic properties of bulk materials. Obviously, the correct prediction of other properties is not warranted and comparison with experiment is necessary