Computer simulation of the atomic structure of defects in metals

Kirsanov, V.V.; Orlov, A. N.

doi:10.3367/ufnr.0142.198402b.0219

Cited by 14 publications

(3 citation statements)

References 24 publications

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“…[2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][27][28][29][30][31][32][33][34][35][36][37]. However, an adequate description of processes occurring with structural changes calls for an MD method that would allow changes in the MD cell parameters.…”

Section: The Molecular-dynamics Methods For Different Statistical Ensementioning

confidence: 99%

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The Molecular-Dynamics Method for Different Statistical Ensembles

2004

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Modifications of the molecular-dynamics method for different statistical ensembles are examined. Particular emphasis is given to the Parrinello-Rahman method wherein the volume and shape of a molecular-dynamics cell are allowed to vary with time. The latter circumstance is of great importance because it enables processes involving marked structural changes in the system to be studied.Computer simulations, as well as real experiments, are an efficient tool of research into the properties and structure of different materials . Among the most popular computer simulation methods are the variational or molecularstatistical method, molecular-dynamics (MD) method, and statistical simulation or Monte-Carlo method.The variational method calls for minimization of the energy of the system as a function of 3N+m variables (N is the number of particles in the system and m is the number of variables describing the MD cell parameters). Determination of a minimum of this composite nonlinear function is rather time consuming and is a nonlinear programming problem from a mathematical standpoint solved by well-known numerical methods. By virtue of its peculiar features (finding the equilibrium stable or metastable state of the system), the variational method is commonly used to obtain information on the structure of the object under study.The Monte-Carlo or stochastical simulation method is applied profitably in investigations of microscopic properties of the system. This method is used to advantage in studying the processes of atomic ordering-disordering, crystal growth, annealing of radiation-induced defects, glide of dislocations over a system of obstacles, etc.The MD method provides a description of the time evolution of the system by means of a system of 6N ordinary differential equations in accordance with Newton's laws of motion. This method has proved to be efficient for calculating the structural properties of point defects, dislocation cores, and grain boundaries and for studying the atomic diffusion processes. In recent years, the MD method has been used in investigations of structural phase transformations in metals and alloys. Adequate simulations of processes involving significant structural changes in the system have been made possible with the development of modifications of the MD method that allow changes in the volume and shape of the MD cell.Below is an overview of modifications of the MD method now in use for different statistical ensembles. THE MOLECULAR-DYNAMICS METHOD FOR DIFFERENT STATISTICAL ENSEMBLESThe MD method is determination of the mechanical trajectory of a system of N particles obeying the following well-known many-body interaction law: 1 2 ( , ,..., ). N V r r rThe simulations proceed from a well-defined microscopic description of the system with the use of a Hamiltonian Н or a Lagragian L to derive the following equations of motion:

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Section: The Molecular-dynamics Methods For Different Statistical Ensementioning

confidence: 99%

“…(6) shows that the driving force for the changes is the difference in the magnitude of the internal and applied stresses. If the stresses are equal, the MD cell parameters reach equilibrium values.…”

Section: The Molecular-dynamics Methods For Different Statistical Ensementioning

confidence: 99%

The Molecular-Dynamics Method for Different Statistical Ensembles

2004

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“…This interaction obeys the laws of conservation of energy and impulse. The sufficient condition for defect formation is the transfer to the atom of the crystal lattice of some amount of energy greater than the threshold energy of the substrate material [29, 30]. Understanding the dynamic processes during surface treatment by a particle flux requires fundamental knowledge of the properties of defects, defect formation in atomic collision processes, and numerous particle–solid interactions.…”

Section: Introductionmentioning

confidence: 99%

The influence of vacancy generation on the impurity distribution in the target under the conditions of surface treatment by a particle beam

Parfenova

Knyazeva

2023

Z Angew Math Mech

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The paper presents a nonlinear coupled isothermal model of the process of surface treatment by a particle beam. The model takes into account the interaction between the diffusion of impurity and propagation of mechanical disturbances, as well as the transfer of the introduced impurity with the vacancy mechanism and under the action of stresses. The nonlinear problem is solved numerically using an implicit symmetric difference scheme of the second order approximation in time and spatial coordinates. The finite time of mass flux relaxation and the dependence of diffusion coefficient on the composition and on the concentration of vacancies lead to peculiarities in the propagation of both the concentration wave and the wave of mechanical disturbances. Vacancy generation contributes to the acceleration of impurity propagation and increased strain/stresses.

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