First-principles study of electronic and elastic properties of EuCd and GdCd

The structural, electronic, elastic and mechanical properties of EuCd and GdCd have been investigated by using first-principles full-potential linearized augmented plane wave (FP-LAPW) method within density functional theory (DFT). The calculations were performed within the generalized gradient approximation (GGA) and local spin density approximation (LSDA) for the exchange–correlation potentials. The ground state properties of these compounds such as the equilibrium lattice parameter (a0), bulk modulus (B) and its pressure derivative (B′) are calculated and compared with available experimental results. The calculated lattice constant obtained with GGA is very close to the experimental values. The electronic structure reveals that these materials exhibit metallic nature. The chemical bonding is interpreted by calculating the electronic charge density plots along (1 1 0) plane which show that EuCd has ionic bonding while GdCd has covalent bonding along with some ionic characteristic. We have determined three independent elastic constants (C11, C12 and C44) at ambient pressure, which have not been calculated and measured yet. Ductility/brittleness of these compounds has been analyzed using Pugh’s rule (B/GH) and Cauchy pressure (C12–C44). Mechanical properties like shear modulus, Young’s modulus, elastic anisotropy and Poisson’s ratio are obtained from the calculated elastic constants. The Debye temperature is also estimated for future investigation.