Molecular-dynamics simulations of glass formation and crystallization in binary liquid metals: Cu-Ag and Cu-Ni

Yue Qi, Tahir Çagin, Yoshitaka Kimura, and William A. Goddard III
Materials and Process Simulation Center, Beckman Institute (139-74), Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125

We used molecular dynamics (MD) to obtain an atomistic description of the melting, glass formation, and crystallization processes in metal alloys. These studies use the quantum Sutton-Chen many-body potentials for Cu, Ni, and Ag to examine the Cu4Ag6 and CuNi alloys. Using cooling rates in the range of 2 × 1012 to 4 × 1014 K/s, we find that CuNi and pure Cu always form a face-centered-cubic (fcc) crystal while Cu4Ag6 always forms a glass (with Tg decreasing as the quench rate increases). The crystal formers have radius ratios of 1.025 (CuNi) and 1.00 (Cu) while the glass former (CuAg) has a ratio of 1.13, confirming the role of size mismatch in biasing toward glass formation.

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