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Structural evolution and atomic dynamics in Ni-Nb metallic glasses: A molecular dynamics study
1International Center for New-Structured Materials (ICNSM), Laboratory of New-Structured Materials, State Key Laboratory of Silicon Materials, and School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, People's Republic of China.
The Journal of Chemical Physics
|October 17, 2017
Summary
Molecular dynamics simulations reveal that icosahedral structures dominate Ni-Nb alloys upon cooling, contributing to their glass-forming ability. Dynamic properties like diffusion and viscosity remain composition-independent, unlike in other alloys.
Area of Science:
- Materials Science
- Computational Materials Science
- Condensed Matter Physics
Background:
- Understanding the static and dynamic structures of alloys is crucial for predicting their properties.
- Nickel-Niobium (Ni-Nb) alloys are of interest for their potential glass-forming abilities.
Purpose of the Study:
- To systematically study the composition and temperature dependence of static and dynamic structures in Ni-Nb alloys.
- To validate a new semi-empirical embedded atom method potential for Ni-Nb system.
Main Methods:
- Molecular dynamics simulations were employed.
- A new semi-empirical embedded atom method potential developed by Mendelev was utilized.
- Analysis included pair correlation functions, structure factor, bond angle distributions, and Voronoi tessellation.
Main Results:
- The potential accurately reproduced experimental data for pair correlation functions and structure factor.
- Icosahedral clusters (⟨0,0,12,0⟩ and distorted ⟨0,2,8,2⟩) become dominant upon cooling, correlating with good glass-forming ability near the eutectic point.
- Self-diffusion coefficients and shear viscosity showed insensitivity to composition during cooling, contrasting with Cu-Zr alloys.
Conclusions:
- The validated potential is reliable for studying Ni-Nb alloys across a range of compositions and temperatures.
- The dominance of icosahedral clusters suggests a specific mechanism for glass formation in Ni-Nb alloys.
- The composition-insensitivity of dynamic properties may stem from the simple phase diagram of Ni-Nb alloys with a single eutectic point.
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