Theoretical investigation of the Cu EOS standard

We calculate the static lattice energy (cold curve), phonon spectrum, and electronic density of states of compressed Cu from electronic structure theory. In the regime 1⩾V/V0⩾0.61⩾V/V0⩾0.6, our ab initio thermal free energy is combined with an empirical static lattice energy based on the measured volume, bulk modulus, and Hugoniot, to give a very accurate complete equation of state. Results are given as analytic expressions for the free energy and a table of P(V,T)P(V,T). The inferred room temperature isotherm supports the proposed modification of the ruby standard of Dewaele et al. [Phys. Rev. B 70 (2004) 094112]. At high compressions (V/V0≲0.5)(V/V0≲0.5), electronic structure theory provides a better estimate of the static lattice energy and room temperature isotherm than extrapolating from the Hugoniot. We give a theoretical room temperature isotherm in the terapascal regime.