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UDC : 621.235 Computer simulation of the spatial construction for silicon nanostructures. Balabay R.M., Chernonog E.Yu. State Pedagogical University, Department of Physics, 54 Prospect Gagarina, Krivoy Rog, 50086, Ukraine. By employing the Method of computer modeling MONTECARLO, the spatial construction of clusters from 10 or 12 atoms of silicon has been revealed. Five atomic flat rings are presented in this structure. Since Suimio Aygima from NEC (Cukubi, Japan) in 1991 year discovered the carbon nanotubes, their synthesis and different studies are gaining the broad scales. Silicon nanosystems are actively researched also, and they have tetrahedral coordination of chemical bond, similar to high energy carbon. In work [1] it is noted that tetrahedral coordination makes any tube of silicon design principally unstable. But then authors [1] show that situation changes if the certain atom of other element in placed in a certain place. Group of Japanese  Indian theorists [1] have calculated atomic and electronic structures of various clusters in Si – Be system, using computer and electronic density functional method. In atomic silicon system it is possible to select the nonflat sixmember ring which configuration reminds an armchair. A chairlike pair gives stable cluster Si_{12}Be_{2 }(with addition of two Be atoms). And now, if to double the number of silicon atoms, having added to a couple of "armchairs", the cluster is transformed: four silicon hexagons become flat, take positions strictly one after another and create the fragment of nanotube with two Be atoms near butt end. This fragment of nanotube can serve as the elementary link, from which the tube of any length can be built. So, the unique characteristics of nanocluster materials are caused by atomic construction, which, because of lack of translation symmetries and exceedingly small samples sizes, is difficult to research applying experimental methods. Hence, computer experiment is crucial in this case. As a basis of it the methods, using analytical interatomic potential functions and start from free configuration and reveal structures, which correspond to characteristic local minimums on the energetic surface, are chosen. Our modeling in the atomic structure of nanoclusters was carried out by means of MonteCarlo method. The StillingerWeber potential was used to calculate the energy of interaction between atoms. MonteCarlo method is a statistical method, that is why, computing experiment is a manyfold repetition of atomic system relaxations. Ten silicon atoms were used to model the structure of nanocluster, at first. The starting atom positions were picked up at random. As an output of significant number of experiments for 10 atoms, two types of pentagonal ring have been got, which are shown on Fig.1. The energy of these two configurations are the lowest among others and approximately equal. The resources of the computer program allowed to observe the construction of cluster from different viewpoints and to find out that five atoms from the ring lied in one plane. Fig. 1. Results in computer modeling for the atomic structure of cluster with 10 silicon atoms. On way of searching for of the configuration with minimum energy for 12 silicon atoms cluster, 6 atoms flat rings were fixed (Fig.2), which on the following step of minimization of energy function reformed in five atomic rings like for cluster out of 10 atoms (Fig.3). Fig. 2. Results in computer modeling for the atomic structure of cluster with 1 2 silicon atoms (intermediate results). Fig. 3. Results in computer modeling for the atomic structure of cluster with 12 silicon atoms (final results). REFERENSES
