First-principles calculations of the structural, elastic, vibrational and electronic properties of YB6 compound under pressure

In this paper, we report our theoretical prediction of a boron-rich binary compound, YB6, with Pm3_m space group subjected to pressures from 0 to 50 GPa. Calculations of first principles are performed to investigate the elastic, vibrational and electronic structural properties using the Density Functional Theory (DFT) within the plane-wave pseudopotential method based on the generalized gradient approximation (GGA) proposed by Perdew-Wang (PW91). We discuss the structural stability based on elastic constants analysis (C-ij) obtained with static finite strain technique. Bulk (B-H), Shear (G(H)) and Young's modulus (E-H) as well as Poisson's ratio (nu), were calculated with the Voigt-Reuss approximation derived from ideal polycrystalline aggregate. Other parameters such as Vickers Hardness (H-v), Pugh's ratio G(H)/B-H, the speed of sound (v(m)) and Debye temperature (theta(D)) were given by elastic modules. We found that C-11 and C-12 elastic constants and elastic modulus monotonically increase while C-44 decrease as a function of pressure; consequently, the structure is dynamically stable and ductile besides that hardness decreases under pressure. The phonon dispersion curves showed no imaginary phonon frequency in the entire Brillouin Zone (BZ) under pressure, showing stable Pm3_m space group. Finally, the density of states (DOS) at the Fermi level decreases with increasing pressure, due to the decrease of the contribution of B 2-p states.