Ab initio study of structural, electronic, elastic and high pressure properties of barium chalcogenides

Abstract

A theoretical studies of structural, electronic, elastic and high pressure properties in barium chalcogenides BaX (X = S, Se, Te, Po) are performed, using the full-potential augmented plane wave plus local orbitals method (FP-APW + lo). In this approach the local-density approximation (LDA) and generalized gradient approximation (GGA) are used for the exchange-correlation (XC) potential. Moreover, the alternative form of GGA proposed by Engel and Vosko (GGA-EV) is also used for band structure calculations. The equilibrium lattice constant and the bulk modulus agree well with the experiments. The pressures at which these compounds undergo structural phase transition from NaCl (B1) to CsCl (B2) phase were found to be in good agreement with the available experimental data. Results obtained for band structure using GGA-EV show a significant improvement over other theoretical work and are closer to the experimental data. A linear relationship is observed between theoretical band gap and 1/a 2 (where a is lattice constant).We have determined the elastic constants C 11 , C 12 and C 44 at ambient conditions in both B1 and B2 structures, which have not been established neither experimentally nor theoretically. Further, we have also calculated the pressure dependence of the elastic constants for the B1 structure of the four compounds.

Ab-initio study of structural, elastic, electronic and thermodynamic properties of BaxSr1−xS ternary alloys

“…The calculated band gaps for all studied compositions (x = 0, 0.25, 0.50, 0.75, 1) are given in Table 3, along with the available experimental and theoretical results. It is clear that for the binary compounds SrS and BaS, the band gap values given by the mBJ scheme are in [7], b [30], c [31], d [9], e [32], f [33], g [8] B* = (C 11 -2C 12 )/3 better agreement with the available experimental results in comparison with the values calculated by PBE-GGA. The modified Becke-Johnson potential (mBJ) as proposed by Tran and Blaha reproduces very well the step structure of the exact exchange potential, which is an important result because only the semi local quantities are used [41].…”

“…The last type of deformation, which yields C 11 + 2C 12 + 4C 44 , is a rhombohedral distortion. The calculated PBE-GGA elastic constants for the Ba x Sr 1−x S ternary [20], c [21], d [22], e [23], f [12], g [7], h [11], i [24], j [9], k [25], l [26], m [27], n [8], o [28] alloys are listed in Table 2. The requirement of mechanical stability in a cubic structure leads to the following restrictions on the elastic constants: C 11 − C 12 > 0, C 11 + 2C 12 > 0, C 11 > 0, C 44 > 0 and C 12 < B < C 11 .…”

“…[34], b [35], c [11], d [36], e [23], f [37], g [38], h [39], i [9], j [28], k [9], l [40] To analyze the physical origins of the band gap bowing, we followed the procedure of Bernard and Zunger [42] and decomposed the bowing parameter into three physically distinct contributions:…”

“…Specifically, Tuncel et al [8] reported the structural, elastic, vibrational and thermodynamic properties of BaX (X = S, Se and Te) using density functional theory (DFT) method. The structural, elastic, and electronic properties of barium chalcogenides have been studied by Bouhemadou et al [9]. Using the full potential linearized augmented plane wave (FP-LAPW) method, Pourghazi et al [10] calculated the reflectivity and imaginary part of the dielectric function for BaSe, BaS and BaTe.…”

FP-LAPW investigation of electronic, magnetic, elastic and thermal properties of Fe-doped zirconium nitride

“…The constants C ij is the measure of response of the crystal to the external forces. The elastic constants C ij is obtained from the structures using a common approach, [24][25][26][27] that is based on the analysis of the changes in the calculated total energy values arising from the changes in strain. A cubic structure has three independent elastic constants C 11 , C 12 , and C 44 .…”