Thermodynamical and phonon properties of rare-earth REBi (RE = Ce and La) bismuthidies

The mechanical, vibrational and thermodynamical properties of rare earth REBi (X = Ce and La) bismuthides in the rocksalt (RS) and CsCl structures are studied by means of a first-principles plane-wave method within the local density approximation (LDA). Moreover, sound velocities and Debye temperature are also obtained successfully. The predicted phonon dispersion curves for these compounds reveal that the CeBi and LaBi are dynamically stable in rocksalt phase. The soft transverse acoustic mode has been correlated with phase transition in these compounds. The variation of lattice-specific heat with temperature obeys the classical Dulong–Petit’s law at high temperature, while at low temperature it obeys the Debye’s T3 law. We also present the electron correlation effects (LDA + U calculation) on lattice parameter and band structures. While the LDA + U results in to the lower lattice parameter values in general the band structures show that the 4f states are closure to the Fermi level.