Density functional theory study of physical properties of nitrides, rare-earth dioxides and silicon-germanium oxynitrides

Abstract

The aim of the present thesis is to study the physical properties of crystalline materials using the density functional theory (DFT) by means of two methods, the full-potential linearized augmented plane-wave plus local orbitals and plane-wave pseudopotential. After presentation of the employed method and its conceptual basis as well as the most recent developments, we will pay more attention to a direct application of the introduced method to compute the structural, electronic and magnetic properties as well as the mechanical stability criteria in different systems. The effect of strong correlation will be undertaken using both of the Hubbard (U) parameter and the spin-orbit coupling. It is worthwhile to see that the rare-earth dioxides need the application of both corrections: U and SOC compared to the rare-earth nitrides, where GGA+U is sufficient to describe correctly the electronic structure. The last application concerns the oxynitrides based on silicon and germanium, where structural, electronic, elastic, electronic optical and dynamical properties are detailed.