Calculation of Combined Diffusion Coefficients of Argon–Copper and Argon–Tungsten Thermal Plasma Mixtures Based on Various Interaction Potentials

Copper (Cu) and tungsten (W) are widely used as electrode materials in thermal plasma devices. Their erosion remains a critical challenge because metal vapors diffuse into the plasma column, significantly altering the plasma composition and, consequently, the thermodynamic, radiative, and transport properties. Accurate prediction of this effect requires reliable transport data, particularly combined diffusion coefficients, which are essential for modeling multicomponent thermal plasmas. Although the combined diffusion coefficient approach has been extensively applied to several plasma mixtures, including argon–copper (Ar–Cu) mixtures, corresponding data for argon–tungsten (Ar–W) mixtures remain unavailable. Furthermore, the available transport data for argon plasmas containing metal vapors are often calculated using approximate interaction potentials to describe collisions between different species, which may reduce their accuracy. In this work, the influence of interaction potential models on combined diffusion coefficients is first investigated for Ar–Cu plasmas, with particular emphasis on neutral–neutral and neutral–ion interactions. The uncertainties associated with commonly used approximate potentials are assessed by comparison with calculations based on more realistic interaction potentials. Subsequently, these more accurate interaction potentials are used to calculate combined ordinary, temperature, and electric-field diffusion coefficients for Ar–Cu and Ar–W thermal plasma mixtures over the temperature range 300–30000 K at a pressure of 1 bar. The results show that the choice of interaction potential significantly affects the combined diffusion coefficients, with a maximum deviation of approximately 52% observed for the combined ordinary diffusion coefficient. Compared with copper, tungsten exhibits lower ordinary but substantially higher temperature diffusion coefficients.