Study of the Structural, Elastic, Electronic and Optical Properties of the Ternary Acetylides A2MC2 (A = Na, K) and (M = Pb, Pt)

We studied the ternary acetylides A 2 MC 2 (A = Na, K) and (M = Pb, Pt) with trigonal structures by using the density functional theory (DFT) as implemented in the CASTEP code. The calculated lattice parameters and atomic fractional coordinates were in agreement with previous calculations and experimental data. A set of isotropic elastic parameters and related properties, namely the module and shear moduli, Young’s modulus, Poisson’s ratio, average sound velocity and Debye temperature were numerically estimated in the frame work of the Voigt-Reuss-Hill approximation. The absorption, energy-loss and dielectric function were calculated. We studied the main contribution to the optical spectra from the transition from the top four valence bands towards the lower three first one of conduction based on the electronic structures.