Computer Modeling of Sodium in the Embedded Atom Model

Abstract

The pair contribution to the potential of sodium in the embedded atom model (EAM) is refined. Two potentials (EAM-2 and EAM-3) that differ in the shape of the embedding potentials are calculated from data on the shock compression and isothermal compression of sodium at 298 K. The main thermodynamic, structural, and diffusion properties of the models are calculated in two variants. The EAM-2 potential poorly describes the properties of sodium at 298 K, while the EAM-3 potential inaccurately characterizes the properties under conditions of shock compression. This means the fixed EAM potential fails to describe the temperature dependence of the properties of the metal. At 900 K, the pressure in the models with the EAM-3 potential is close to the data obtained ab initio. There is no prepeak of the pair correlation function of sodium, but the anomalous behavior of the pressure of the sodium bcc lattice at ∼19–25 GPa is confirmed. The melting lines in the sodium models are calculated in two variants with maxima at around 30 GPa. The problem of the predictive power of the embedded atom model is discussed.