High pressure melting and equation of state of aluminium

Abstract Melting curve of aluminium has been determined up to 50 GPa in a diamond anvil cell with laser heating. Using wavelength independent emissivity very good agreement was found with previous melting study, theoretical calculations and shockwave experiments. Analysis of the data using Lindemann and Simon melting equations suggests that melting occurs close to, but not exactly at the same pressure as measured at the cold state. Grueneisen parameter γ scales with volume as γ/γ0=V/V0, where γ0=2.2 ± 0.1, a value close to 2.14 from adiabatic decompression experiments. The melting curve, when transformed to normalized coordinates, verifies the prediction of work of Schlosser et al. [Phys. Rev. B, 40 (1989) 5929] for the linear relationship between normalized melting temperature and normalized pressure. Fit of the combined data from melting, thermal expansion, room compression, and shockwave studies to the Mie–Grueneisen thermal equation of state gives γ0=2.42 ± 0.02; Anderson’s thermal pressure model yields −0.032 ± 0.001 and −0.001 ± 0.001 GPa/K for the temperature derivative of isothermal bulk modulus at constant pressure and constant volume, respectively.