Ab-initio calculations and phase diagram assessments of An–Al systems (An = U, Np, Pu)

The enthalpies of formation of binary intermetallic compounds AnAln ( n = 2 , 3 , 4 , An = U,Np,Pu ) were assessed from first principle calculations of total energies performed using full potential APW + lo technique within density functional theory (WIEN2k). The substantial contribution to entropies, S 298 ° , arising from lattice vibrations was calculated by direct method within harmonic crystal approximation (Phonon software + VASP for obtaining Hellmann–Feynman forces). The electronic heat capacity and the corresponding contribution to entropy were estimated from the density of states at Fermi level obtained from electronic structure calculations. The phase diagrams of the relevant systems An–Al were calculated based on the thermodynamic data assessed from ab-initio calculations, known equilibrium and calorimetry data by employing the FactSage program.