Abstract:
Two new potentials are proposed for the embedded-atom model for nickel: one that includes the thermal contribution of electrons to the energy and one that disregards it. The potential parameters are found based on the nickel properties in isobar $p = 0$ and under shock compression with pressures up to $\sim760$ GPa. The best consistency with experimental data is obtained when the electron contribution to the energy is taken into account. The calculated Hugoniot adiabat is in good agreement with the true curve. The inclusion of the electron contribution significantly reduces temperature on the adiabat and increases the cold pressure. The calculated melting curve of the nickel models gradually goes up to $4518$ K at $300$ GPa and is barely affected by the presence of the electron contribution. The coordinates of the melting section on the shock adiabat are determined (starting at $275.8$ GPa and $4422$ K and finishing at $297.6$ GPa and $4499$ K). The phase diagram of nickel with a stable bcc phase region at pressures above $110$–$130$ GPa is proposed. Tables with the energies and pressures of the models at compression ratios up to $1.8182$ are presented.
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