Theoretical investigation of elastic and phononic properties of Zn1−xBexO alloys

Abstract

Our calculations were conducted within density functional theory (DFT) and density functional perturbation theory (DFPT) using norm-conserving pseudo-potential and the local density approximation. The elastic constants of Zn1−xBexO were calculated, C11, C33 and C44 increase with the increase of Be content, whereas the C12 shows a nonmonotonic variation and C13 decreases when Be concentration increases. The values of bulk modulus B, Young’s modulus E and shear modulus G increase with the increase of Be content. Poisson’s ratio σ decreases with increased Be concentration. The ductility decreases with increasing Be concentration and the compressibility for Zn1−xBexO along c-axis is smaller than along a-axis. Phonon dispersion curves show that Zn1−xBexO is dynamically stable (no soft modes). Quantities such as refractive index, Born effective charge, dielectric constants and optical phonon frequencies were calculated as a function of the Be molar fraction x. The agreement between the present results and the known data that are available only for ZnO and BeO is generally satisfactory. Our results for Zn1−xBexO (0 < x < 1) are predictions.