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    A molecular dynamic study of the effects of high pressure on the structure formation of liquid metallic Ti62Cu38 alloy during rapid solidification
    (Elsevier, 2021) Domekeli, Unal
    In this study, the effects of high pressure ranging from 0 to 100 GPa on the structural evolution of liquid metallic Ti62Cu38 alloy during rapid cooling have been extensively investigated by using classical molecular dynamics simulation with embedded atom method at a cooling rate of 5 x 10(10) K s(-1). To investigate the first order phase transition during the solidification of the system and to determine the crystallization and glass transition temperatures, the temperature-dependent change in the curves of thermodynamic properties such as average volume per atom, specific heat and enthalpy are examined. Structural properties are expressed by using pair distribution functions, structure factors and atomic configuration. The microstructural atomic order in the system are characterized by using Honeycutt-Andersen pairs and Voronoi tessellation analysis methods. The results provide convincing evidence that the applied pressure during rapid cooling has a strong effect on determining whether the metallic liquid Ti(62)Cu(3)8 will transform into a crystal-like structure or a glassy structure. The critical pressure for the glass formation are predicted to be approximately 10 GPa. While the simulated crystallization and glass transition temperatures increase linear with a slope of 11.11 K GPa(-1) within the range of 0-9 GPa and with a slope of 12.10 K GPa(-1) within the range of 10-100 GPa, respectively. While crystal-like clusters are dominant in the system up to 10 GPa, icosahedral-like clusters representing a short range order at 10 GPa become dominant in the system. The amount of dominant icosahedral-like clusters remains basically stable with pressure increase from 10 to 100 GPa. Also, as the pressure is applied, the calculated bond lengths for all bond pairs decrease.
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    Molecular dynamics study of structure and glass forming ability of Zr70Pd30 alloy
    (Springer, 2016) Celtek, Murat; Sengul, Sedat; Domekeli, Unal; Canan, Cem
    In this study, the temperature effects on the structural evolution of the Zr70Pd30 binary alloy in the glassy and liquid states were studied using the molecular dynamics simulations based on the many-body type tight-binding potential. We considered the following properties in detail: the temperature dependence of the volume, the partial and total pair distribution functions and the simulated glass transition temperature. The effects of the cooling rates on the glass transition temperature were examined. The Wendt-Abraham parameter was calculated to determine the glass transition temperature of Zr70Pd30 glassy alloy. The pair analysis technique of Honeycutt-Andersen was applied to define local atomic arrangements produced from molecular dynamics simulations. The results show that the icosahedral ordering in glassy state has been composed during quenching period, and the simulated glass transition temperature and the total pair distribution functions are in good agreement with the experimental data.