Physical properties of the body-centred tetragonal

Abstract

We have investigated the structural, elastic, electronic, and lattice dynamical properties of (Formula presented.) in the body-centred tetragonal (Formula presented.) structure using a generalised gradient approximation of the density functional theory and the ab initio pseudopotential method. The calculated second-order elastic constants indicate that (Formula presented.) is mechanically stable and behaves in a ductile manner. Our electronic results show that the states close to the Fermi level are primarily contributed by Pd d and Ge p orbitals. A detailed analysis of electron–phonon interaction calculations reveals that the mechanism for superconductivity in (Formula presented.) is mainly governed by interactions of Pd d and Ge p electrons around the Fermi level with acoustic phonon modes and low-frequency optical phonon modes, which strongly change PdGe(Formula presented.) tetrahedral bond angles. The values of the average electron–phonon coupling constant and the logarithmic average frequency are calculated to be 0.66 and 77.3 K, respectively. Inserting these values into the Allen–Dynes formula with using an acceptable value of (Formula presented.) for the effective Coulomb repulsion parameter, the value of superconducting transition temperature is obtained to be 1.69 K, which is in excellent agreement with its experimental value.