Amorphous alloys have become a research hotspot since their inception due to their excellent physical and chemical properties. Ni Zr amorphous alloy has attracted widespread attention from researchers due to its excellent mechanical properties and good amorphous formation ability. However, further research is needed on its formation mechanism and factors affecting its amorphous formation ability. Among them, significant progress has been made in using molecular dynamics (MD) simulations to analyze the microstructure and glass transition behavior of alloy melts and metallic glasses.

Pan Shaopeng and others from Taiyuan University of Technology used molecular dynamics simulation method, with Ni Zr as the initial model, to analyze the volume changes during the cooling process, as well as the thermodynamic parameters and related structural parameters of the high-temperature melt, and to analyze the factors affecting its amorphous formation ability. The relevant research results have been published in Functional Materials.

Researchers used classical molecular dynamics simulation methods and the Finnis Sinclair empirical potential function in LAMMPS to analyze the microscopic atomic structure and related thermodynamic properties of Ni Zr alloys with different compositions. The initial configuration selects 1000000 atoms randomly distributed according to their composition ratios, and periodic boundary conditions (PBCs) are used for all dimensions. The entire simulation process uses an isothermal isobaric ensemble (NPT, P=0), with a constant pressure set at 0 GPa and a simulation step size of 0.1 fs. First, relax for 1 ns at a high temperature of T=2500K, then cool down to 10K at a constant cooling rate of 10¹²K/s, and finally relax for 1 ns at a temperature of 300K. Each model outputs a configuration file every 10000 steps to obtain the initial sample of Ni Zr alloy. Calculate the variation of volume with composition during the cooling process of the sample, and analyze the atomic structure parameters and thermodynamic properties of Ni Zr alloy high-temperature melt using the configuration file output at 2500K. The results show that the amorphous formation ability of Ni Zr alloy gradually decreases and then gradually recovers in the range of Ni content accounting for 60% to 90%. The amorphous formation ability is weakest at Ni content accounting for 75% (Figure 1). The three thermodynamic parameters of mixing enthalpy, mixing entropy, and mixing free energy show a unidirectional variation in the range of Ni content accounting for 60% -90%, and do not show a significant correlation with the change in amorphous formation ability (Figure 2). The second-order partial derivative of the mixed free energy first increases and then decreases, and the change in thermodynamic factors is significantly correlated with the amorphous formation ability of Ni Zr alloy, which first weakens and then strengthens. The second peak of the Zr Zr binary distribution function with Ni accounting for 75% exceeds the first peak, and the slight increase and then decrease in the highest coordination number around Ni and Zr atoms may be related to the change in the amorphous formation ability of Ni Zr alloy, which first weakens and then strengthens (Figure 3). The Warren Cowley parameter of Ni Zr bond first increases in negative value and then decreases in negative value, and the bond length of Ni Zr bond first decreases and then increases, which is consistent with the trend of weakening and then strengthening the amorphous formation ability of Ni Zr alloy (Figure 4). The change in the binding ability between Ni atoms and Zr atoms affects the amorphous formation ability of Ni Zr alloys. This study is beneficial for deepening the understanding of the relationship between high-temperature melt and amorphous formation ability of alloys.