Molecular-Dynamic Research of the Structure of Amorphous Ni

Gennadiy M. Poletaev ,  Mikhail D. Starostenkov ,  Vladimir Y. Krasnov 

Altai State Technical University (ASTU), Lenin st.46, Barnaul 656038, Russian Federation

Abstract

The paper is devoted to the research by the method of molecular dynamics of the structure of amorphous Ni obtained by superrapid cooling from melted state using the method of molecular dynamics. Main purpose of the research was the determination of the structure of amorphous metal in the dependence on the velocity of cooling by the separation of known structural elements (elementary cells of FCC and HCP, Frank-Kasper polyhedrons, tetrahedrons). The calculated block of Ni contained 13500 atoms in a molecular-dynamic model. The researches were made using two types of potentials of interatomic interaction: Morse pair potential and many-particle Cleri-Rozato potential. Three different velocities of Ni cooling from the melted state: 10^13, 10^14 and 10^15 K/s were considered. The method of cooling was in the corresponding decrease of atomic velocities at every iteration of the computer experiment. It was found in the paper that amorphous metal can have minimum two variants of structure in the dependence on the velocity of cooling from melt. Ni structure at the cooling velocities 10^14 - 10^15 K/s consisted of conjugated and differently deformed tetrahedrons. In that case, the structure had “nuclei of idealness” - clusters formed of two or three conjugated ideal tetrahedrons. Less ideal tetrahedrons were located around ideal ones. Deformation of tetrahedrons increased with the removal from “the nuclei of idealness”. The average distance between “nuclei” was about 10 Å. Frank-Kasper phase consisting of conjugated and opposite deformed icosahedrons formed at the cooling velocity of the melt of 10^13 K/s order. The formation of FCC and HCP nanocrystals competing with Frank-Kasper phase takes place at the given velocity of cooling. Concentration of 14- and 15-vertex polyhedrons of Frank-Kasper was very small and did not exceed 0.1 % 16-vertex polyhedrons were not observed.

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Presentation: Oral at E-MRS Fall Meeting 2009, Symposium H, by Mikhail D. Starostenkov
See On-line Journal of E-MRS Fall Meeting 2009

Submitted: 2009-05-08 08:12
Revised:   2009-06-07 00:48
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