Thermodynamics of the α-γ transition in cerium from first principles

We present a thermodynamical investigation of the alpha= beta transition of Ce using density functional theory within the projector augmented wave framework combined with the dynamical mean field theory. First, we confirm that without spin-orbit coupling no transition appears at zero temperature. Second, we extend the same conclusion to finite temperature with a slight difference: a crossover is observed both in temperature and pressure between the alpha and gamma phases. This is obviously visible as a softening of the bulk modulus. Third, we show the leading role of entropy for the description of the equation of state of cerium. Last, we discuss the role of spin coupling, and we argue that neglecting the spin-orbit coupling is roughly equivalent to a renormalization of temperature. Indeed, at 800 K, both our variation of thermodynamical quantities and our spectral functions describe the experimental data.