Correlation entropy and its relation to properties of liquid iron, cobalt and nickel

Abstract

We present entropy calculations of liquid Fe, Co and Ni over an extended temperature range of approximately 200 K above the melting point. The theory we use is based on a systematic expansion of the entropy in terms of the partial N-particle distribution functions given first by Green for the canonical ensemble. First, we calculate the pair and triplet correlation entropies using measured diffraction data. To evaluate the triplet correlation entropy, we did not use the superposition approximation of Kirkwood in this work. Next, we calculate the self-diffusion coefficient based on Dzugutov's scaling law using the pair and triplet correlation entropies. Then we estimate the viscosity coefficient and the surface tension for these liquid metals using the Stokes–Einstein relation, the Born–Green equation and Fowler's formula for the surface tension. Predicted values of the self-diffusion coefficient, the viscosity coefficient and the surface tension are reasonable in comparison with available experimental data.