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

Abstract

In this paper, we report our theoretical prediction of a boron-rich binary compound, YB6, with Pm3m 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 (BH), Shear (GH) and Young's modulus (EH) as well as Poisson's ratio (ν), were calculated with the Voigt-Reuss approximation derived from ideal polycrystalline aggregate. Other parameters such as Vickers Hardness (Hv), Pugh's ratio GH/BH, the speed of sound (vm) and Debye temperature (θD) 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 Pm3m 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.

Coexistence of superconductivity and charge density wave instability in A15-Nb3Sn

“…Our results are consistent with previous studies reporting that the transition temperature is a function of N(E F ). 55,56 Additionally, the observed shift of the Fermi level and reduction of the DOS peak near E F are similar to the examples of electron dopingsuppressed CDW phases. 57,58 These results suggest that the suppression of the CDW phase may be controlled by the shift of E F and the reduction of N(E F ) near the Fermi level.…”

First-principles study of the effect of pressure on the physical properties of PbC

“…The brittle or ductile character of a material can be evaluated using the empirical criteria of the Pugh's ratio (K ). A material is brittle if > K 0.5, but ductile if < K 0.5 [42]. The Poisson's ratio (ν) gives us signals of the type of structure.…”

“…For covalent crystals n < 0.2, for ionic-covalent crystals n   0.2 0.3 and for metals n  0.33 [43]. Additionally, the hardness can be studied by means of the Vickers hardness (H V ) [42] . The K, ν, and H V values can be obtained utilizing:…”

A First-Principles Investigation on the Electronic and Mechanical Properties of 1T TiSe2 Multilayers for Energy Storage

“…The 2D Young's modulus (in-plane stiffness) for the strains along the [100] and [010] directions are [58][59][60] : The Pugh relation (G/B) and Poisson's ratio (v) were calculated from the Bulk (B) and Shear (G) modulus and elastic constants (C ij ). The Poisson's ratio and the Vickers hardness (H v ) can be obtained using the formula 55,[61][62][63] :…”