Equation of State and Viscosity of Tantalum and Iron from First Principles

To understand and model at continuum level the high-energy-density dynamic response in transition metals like Tantalum and Iron, as it arises in hypervelocity impact experiments, an accurate prediction of the underlying thermodynamic and kinetic properties for a range of temperatures and pressures is of critical importance. The relevant time scale of atomic motion in a dense gas, liquid, and solid is accessible with \textit{ab-initio} Molecular Dynamics (MD) simulations. We calculate EoS for Ta and Fe via Thermodynamical Integration in 2D (V,T) phase space throughout different single and two-component phases. To reduce the \textit{ab-initio} demand in selected regions of the space, we fit available gas-liquid data to the Peng-Robinson model [1] and treat the solid phase within the Boxed-quasi-harmonic approximation [2]. In the fluid part of the 2D phase space, we calculate shear viscosity via Green-Kubo relations, as time integration of the stress autocorrelation function. \\[4pt] [1] Ind. Eng. Chem., Fundam \textbf{15}, 59 (1976) \\[0pt] [2] A. van de Walle and G. Ceder, \textit{Rev. Mod. Phys.} \textbf{74} 11 (2002)