Ab initio study of structural, elastic and vibrational properties of praseodymium chalcogenides

The plane-wave pseudopotential approach to the density-functional theory within the GGA approximation implemented in Vienna Ab-initio Simulation Package (VASP) code have been used to calculate structural, elastic and lattice dynamical properties of praseodymium chalcogenides: PrS, PrSe and PrTe. The structural properties are performed in five different crystal structures: NaCl (space group Fm3m(225)), CsCl (space group Pm3m(221)), ZB (space group F43m(216)), WC (space group P6m2(187)) and CuAu (P4/mmm(123)). Our results showed that these chalcogenides are stable in NaCl phase which are in agreement with the experimental works. The phonon dispersion curves are showed that the gap between the optic and acoustic branches decreases on going from PrS to PrTe. We have also estimated some thermodynamical properties such as entropy and heat capacity at the temperature range 0–1000 K.