Density functional theory study of the structural and electronic properties of Mg₃Bi₂in hexagonal and cubic phases

Abstract

We study the structural and electronic properties of Mg3Bi2 in both hexagonal and body center cubic (bcc) phases by using first-principles calculations based on the density functional theory (DFT). We solve the Kohn-Sham equations using the full potential linearized augmented plane wave (FP-LAPW) method. The generalized gradient approximations as proposed by Perdew-Burke-Ernzerhof (PBE sol GGA) and Engel-Vosko (EV-GGA) are employed to calculate the exchange correlation potential. Using GGA, we compute the optimized lattice parameters of the bcc. This is the first instance of such application of GGA. In close agreement with experimental results, our electronic calculations show that the hexagonal phase is a direct gap semiconductor with energy gap of 0.2520 eV. The bcc phase calculated band structure shows a direct gap semiconductor with band gap of 1.0306 eV. We further study the effects of applying pressure on the band structure of the system.

Studying Static, Dynamic and Transport Properties of Mg3Bi2

“…Zhou et al [15] have found the cohesive energy 2575.36 kJ/mol from rst principle calculations. The calculated lattice parameters at room temperature are in fairly good agreement with available theoretical and experimental data [10,15,16,18,2224]. All values of lattice parameters are given in Table II.…”

“…Lattice parameters are calculated as a = 4.61 Å and c = 7.24 Å and compared with a considerable amount of experimental and rst principle data [10,15,16,18,2224] which are in agreement with these results (Table II). As the temperature increases from room temperature to 1600 K, constant stress method of Parrinello and Rahman dynamics is used where lattice parameters change in each dimension so that lattice constant a 1 and a 2 diverge from each other and angles do not maintain their α = 90…”

“…Potential parameters are given in Table I. Parameters were adjusted to reproduce experimental data like lattice constants, bulk modulus and elastic constants where lattice constant is an experimental value [10,18] and elastic properties are from rstprinciple calculations [15,16]. Moreover, the Bredig (440) phase transition of Mg 3 Bi 2 has been taken into account while obtaining potential parameters.…”

“…All the elastic properties are investigated by GULP program [27]. To the best of our knowledge there are only two measured values of α-Mg 3 Bi 2 bulk modulus [15,16]. Both of them are rstprinciple calculations and dierent from each other by about 15%.…”

“…First principles molecular dynamics simulation of liquid Mg 3 Bi 2 has also been calculated by Wijs [9] and Hao et al [14]. Structural and elastic properties of solid Mg 3 Bi 2 is calculated by Zhou et al [15] and Sedighi et al [16] by rst-principles calculations.…”