Engin Ateser

STRUCTURAL, MECHANICAL AND LATTICE DYNAMICAL STABILITY OF AgC AND AuC COMPOUNDS: A FIRST PRINCIPLES STUDY

Based on density functional theory, we have studied the structural stability, elastic, mechanical and lattice dynamical properties of AgC and AuC compounds for various structures: NaCl (B1), CsCl (B2), ZnS (B3), wurtzite (B4), WC (Bh), NiAs (B81) and CdTe. Generalized gradient approximation has been used for modeling exchange-correlation effects. The second-order elastic constants and related polycrystalline properties (bulk modulus, shear modulus, Youngs modulus, Poissons ratio, Debye temperature and sound velocities) have been calculated and discussed. We have also calculated phonon dispersion and phonon density of states of these compounds in all considered structures. According to the results, we found that, AgC compound is mechanically and dynamically stable in B81, B1 and B4 structures. Our results indicate that B81 and B3 are the candidate stable structures energetically, mechanically and dynamically for AgC and AuC compounds, respectively.

THE FIRST-PRINCIPLES STABILITY STUDY OF PdC AND CdC COMPOUNDS

We have studied structural, mechanical and dynamical properties of PdC and CdC compounds to predict the most stable structure. We have focused on seven binary structure types as rock salt (RS), caesium chloride (CsCl), zinc blende (ZB), wurtzite (WZ), tungsten carbide (WC), cadmium telluride (CdTe) and nickel arsenide (NiAs). For modelling exchange-correlation effects we have used generalized gradient (GGA) approximation based on Perdew–Burke–Ernzhorf functional (PBE). The polycrystalline elastic moduli such as Youngs and shear moduli, Poissons ratio, sound velocities, Debye temperatures and shear anisotropic factors have been presented for mechanically stable structures using second-order elastic constants calculated from the stress-strain relations. The results show that PdC is thermodynamically, mechanically and dynamically stable in ZB structure. On the other hand, while CdC is energetically in favor of RS structure, it is mechanically and dynamically stable in ZB structure.