First-Principles Calculations of Structural, Electronic, Optical, and Thermoelectric Properties of LuNiBi and LuNiSb Half-Heusler

Abstract

The structural, electronic, optical, and thermo-electric properties of LuNiBi and LuNiSb Half-Heusler have been studied using a full potential linearized augmented plane-wave (FP-LAPW) method. The results of the calculations presented in this work were obtained through the use of different approximations GGA-PBE, GGA-PBEsol, GGA-WC, and mBJ-GGA. The electronic band structures exhibit that the LuNiBi and LuNiSb alloys have a small indirect gaps in the valence band and the conduction band at points Г and X, revealing the semiconductor character in both compounds. The complex dielectric function ε (ω), optical conductivity σ (ω), extinction coefficient к (ω), refractive index n (ω), and reflectivity R (ω) as a function of photon energy are calculated using mBJ-GGA approximation, that is yielding results in good accordance with available experimental data. On the other hand, the variations of the thermal conductivity, power factor, figure of merit ZT, Seebeck coefficient, and electrical conductivity, as a function of temperature, have been investigated. Most of the optical and thermoelectric properties of LuNiSb and LuNiBi materials are not available in the literature; this makes the present work as a detailed comparative study between both compounds and opens the path for other future accurate theoretical studies to find the promising substitute for the interesting and more efficient thermoelectric device in industry.

Comprehensive investigation of electronic structure, phonon spectrum and thermoelectric performance of LuMSb (M = Ni, Pd, Pt) half Heusler compounds from first principles

“…For LuPtSb the electronic states of the VB and CB just touch the Fermi level ( E F ) at the Γ point of the Brillouin zone which shows it is a gapless semiconductor. Our calculated values of E g are in good agreement with experimental 27,32,40,41 and other theoretical 34,35,37,48,49 results and are presented in Table 2. We found that by the replacement of Ni by Pd and then Pd by Pt, the value of band gap decreases.…”

“…49 6.451 49 Note: Available results from experiments and other calculations are also listed. with experimental 27,32,40,41 and other theoretical 34,35,37,48,49 results…”

“…Figure 2A–C presents the volume optimization curve with respect to total energy variation to obtain optimized structural parameters after solving Murnaghan's equation of state. Optimized structural parameters such as lattice parameter ( a o ), primitive unit cell volume ( V o ), Bulk modulus ( B o ) and pressure gradient of Bulk modulus ( B o ′) corresponding to the minimum total energy ( E o ) of the compounds are listed in Table 1 along with other calculated 34,48 and experimental 26,27,40,41 results. Obtained structural lattice parameters are overestimated by ~1.5% with experimental data 26,27,40,41 .…”

“…The GGA + U approximation 44 with the inclusion of the spin-orbit coupling (SOC) effect was used to include exchange correlation for an appropriate calculation. The selfconsistent spin polarized BS calculations were executed with 4000 kpoints in the irreducible Brillouin zone and using energy convergence 1 along with other calculated 34,48 and experimental 26,27,40,41 results. Obtained structural lattice parameters are overestimated by $1.5% with experimental data.…”

Electronic, structural and optical properties of rare-earth based TbNiSb half Heusler compound

“…It crystallizes in MgAgAs type structure, with space group F43m (216) and the atomic positions of Tb, Ni, and Sb atoms are (0,0,0), (1/4,1/4,1/4) and (1/2,1/2,1/2), respectively. Various experimental and theoretical studies on HH compound have been reported [11][12][13][14][15][16]. Ciesielski et al [11] experimentally studied the high temperature thermoelectric application of HH RENiSb (RE= Sc, Dy, Ho, Er, Tm, Lu) compounds and concluded that by properly adjusting carrier concentration and lowering their thermal conductance through appropriate alloying or nano structuring, the RENiSb phases are excellent candidates to provide great thermoelectric efficiency at high temperatures.…”