High-temperature thermophysical properties of liquid zirconium: Quantum molecular dynamics and pulse heating experiment

This study presents a joint first-principles and experimental investigation of the thermophysical properties of liquid zirconium at high temperatures. An ab initio estimate of the critical point parameters of zirconium is obtained: ${T}_{c}=9.4\ifmmode\pm\else\textpm\fi{}0.1\phantom{\rule{4pt}{0ex}}\mathrm{kK}$, ${\ensuremath{\rho}}_{c}=1.38\ifmmode\pm\else\textpm\fi{}0.1\phantom{\rule{4pt}{0ex}}\mathrm{g}/{\mathrm{cm}}^{3}$, and ${P}_{c}=3.35\ifmmode\pm\else\textpm\fi{}0.4$ kbar. In addition, we analyze various thermodynamic properties, including thermal expansion, isochoric and isobaric heat capacity, the Gr"uneisen parameter, and the speed of sound in liquid zirconium along the critical isobar, providing approximation dependencies that align with experimental measurements. We also present a tabulated ab initio equation of state for Zr in the liquid and supercritical regions. Experimental data from rapid electrical pulse heating of zirconium wires confirm the low fusion enthalpy and the isobaric heat capacity dependence predicted by our quantum molecular dynamics (QMD) simulations. The resistivity of solid and liquid zirconium up to 6 kK is also measured and its significant increase in the critical region is shown using the Kubo-Greenwood formula. Calculated normal spectral emissivity shows almost constant behavior up to 4 kK with a significant increase at higher temperatures.