Viscosity of Cobalt Melt: Experiment, Simulation, and Theory

TL;DR

This study combines experimental, simulation, and theoretical methods to analyze the viscosity of cobalt melt across a wide temperature range, providing new insights into its temperature dependence and activation energy.

Contribution

It presents a comprehensive approach integrating experiments, molecular dynamics simulations, and theoretical models to accurately determine cobalt melt viscosity and its temperature dependence.

Findings

Good agreement between experimental, simulation, and theoretical viscosity results.

Determined activation energy of cobalt melt viscosity as (5.38±0.02)×10^{-20} J.

Provided theoretical expressions for stress tensor correlation and viscosity based on system parameters.

Abstract

The results of experimental measurements, molecular dynamics simulation, and theoretical calculations of the viscosity of a cobalt melt in a temperature range of $1400-2000$~K at a pressure $p=1.5$~bar corresponding to an overcooled melt at temperatures of $1400-1768$~K and an equilibrium melt with temperatures from the range $1768-2000$~K are presented. Theoretical expressions for the spectral density of the time-dependent correlation function of the stress tensor $\tilde{S}(\omega)$ and kinematic viscosity $\nu$ determined from the frequency and thermodynamic parameters of the system are obtained. The temperature dependences of the kinematic viscosity for the cobalt melt are determined experimentally by the torsional oscillation method; numerically, based on molecular simulation data with the EAM potential via subsequent analysis of the time correlation functions of the transverse current in the framework of generalized hydrodynamics; and by the integral Kubo-Green relation; they were also determined theoretically with the Zwanzig-Mori memory functions formalism using a self-consistent approach. Good agreement was found between the results of theoretical calculations for the temperature dependence of the kinematic viscosity of the cobalt melt using experimental data and the molecular dynamics simulation results. From an analysis of the temperature dependence of the viscosity, we obtain an activation energy of $E=(5.38\pm0.02)\times10^{-20}$~J.