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Civil-Comp Proceedings
ISSN 1759-3433
CCP: 84
Edited by: B.H.V. Topping, G. Montero and R. Montenegro
Paper 185

Computer Simulation of Nanoelements: Formation, Interaction and Self-Organization

A.V. Vakhrouchev12 and A.A. Vakhrouchev13

1Department of Molecular Mechanics, Institute of Applied Mechanics,
Ural Branch of the Russian Academy of Science
2Department of Heat Engines and Equipment,
3Department of Computer Science Systems,
Izhevsk State Technical University, Izhevsk, Russia

Full Bibliographic Reference for this paper
A.V. Vakhrouchev, A.A. Vakhrouchev, "Computer Simulation of Nanoelements: Formation, Interaction and Self-Organization", in B.H.V. Topping, G. Montero, R. Montenegro, (Editors), "Proceedings of the Fifth International Conference on Engineering Computational Technology", Civil-Comp Press, Stirlingshire, UK, Paper 185, 2006. doi:10.4203/ccp.84.185
Keywords: nanoelements, nanoparticles, structure, interaction, computer simulation.

One of the main tasks in making nanocomposites is building the dependence of the structure and shape of the nanoelements forming the basis for the composite of their sizes. This is because with an increase or a decrease in the specific size of nanoelements their physical-mechanical properties such as the coefficient of elasticity, strength, deformation parameter, etc. vary by over one order .The calculations and experiments show that this is primarily due to a significant rearrangement of the atomic structure and the shape of the nanoelement. The experimental investigation of the above parameters of the nanoelements is technically complicated and laborious because of their small sizes. When the characteristics of powder nanocomposites are calculated it is also very important to take into account the interaction of the nanoelements since the changes in their original shapes and sizes in the interaction process and during the formation of the nanocomposite can lead to a significant change in its properties and a cardinal structural rearrangement. In addition, the experimental investigations show the appearance of the processes of the ordering and self-assembling leading to a more organized form of a nanosystem. The above phenomena play an important role in nanotechnological processes. They allow nanotechnologies to be developed for the formation of nanostructures by the self-assembling method (which is based on self-organizing processes) and building up complex spatial nanostructures consisting of different nanoelements.

The investigation of the above dependences based on the mathematical modeling methods requires the solution of the aforementioned problem at the atomic level. This requires large computational aids and computational time, which makes the development of economical calculation methods urgent. The objective of this work was the development of such a technique.

In the paper, the methods of numerical modeling within the framework of molecular mechanics and dynamics were used for investigating the regularities of the amorphous phase formation and the nucleation and spread of the crystalline or hypocrystalline phases over the entire nanoparticle volume depend on the process parameters, nanoparticles sizes and the ambient thermodynamic conditions. Also the method for calculating the interactions of nanostructural elements is offered, which is based on the potential built up with the help of the approximation of the numerical calculation results using the method of molecular dynamics of the pairwise static interaction of nanoparticles. Based on the potential of the pairwise interaction of the nanostructure elements, which takes into account forces and moments of forces, the method for calculating the ordering and self-organizing processes has been developed. The investigation results for the self-organization of the system consisting of two or more particles are presented and the analysis of the equilibrium stability of various types of nanostructures has been carried out.

The problem includes three main stages: the first stage is building the internal structure and the equilibrium configuration (shape) of each separate non-interacting nanostructure element; the second stage is calculating the pairwise interaction of two nanostructure elements; and the third stage is establishing the regularities of the spatial structure and evolution with time of the nanostructure as a whole.

In conclusion, the following basic regularities of the nanoparticle formation and self-organization should be noted.

  1. The existence of several types of the forms and structures of nanoparticles is possible depending on the thermodynamic conditions.
  2. The absence of the crystal nucleus in small nanoparticles.
  3. The formation of a single (ideal) crystal nucleus defects on the nucleus surface connected to the amorphous shell.
  4. The formation of the polycrystal nucleus with defects distributed among the crystal grains with low atomic density and change interatomic distances. In addition, the grain boundaries are non-equilibrium and contain a great number of grain-boundary defects.
  5. When there is an increase in sizes, the structure of nanoparticles changes from amorphous to roentgen-amorphous and then into the crystalline structure.
  6. The formation of the defect structures of different types on the boundaries and on the surface of a nanoparticle.
  7. The nanoparticle transition from the globe-shaped to the crystal-like shape.
  8. The formation of the "regular" and "irregular" shapes of nanoparticles depending on the number of atoms forming the nanoparticle and the relaxation conditions (the rate of cooling, first of all).
  9. The structure of a nanoparticle is strained because of the different distances between the atoms inside the nanoparticle and in its surface layers.
  10. The system of nanoparticles can to form stable and unstable nanostructures.

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