Molecular Dynamics Study of Thermodynamics and Structure of Liquid Sodium under Pressure

By the molecular dynamics method using 864 atoms the structural and thermodynamic properties of liquid Na are calculated for two states on the melting curve, which correspond to compressions u = 0 and u ≈ 20%. The radial distribution function g(r), structure factor S(k), energy U, and pressure p are found. Both, g(r) and S(k) are similar in the two states and differ mainly in a simple compression of all the scales. This similarity is in agreement with the hypothesis of the existence of the “crystallization criterion”, the universality of the short-range order on the melting curves for simple liquids. A comparison with the Pereus-Yevick (PY) approximation for S(k) shows that at u = 0 SPY(k) is close to SMD(k) and to the experiment, while at u ≈ 0.2 SPY(k) and SMD(k) diverge sharply, which is, apparently, due to the decreasing of the accuracy of the PY approximation at considerable values of u. [Russian Text Ignored.]