Structural, optoelectronic, thermodynamic and thermoelectric properties of double half Heusler (DHH) Ti2FeNiSb2 and Ti2Ni2InSb compounds: A TB-mBJ study

Abstract

Structural, electronics, optical, thermodynamic, as well as thermoelectric characteristics of the double half Heusler (DHH) Ti2FeNiSb2 and Ti2Ni2InSb compounds were considered by employing the density functional theory (DFT) having the generalized gradient approximation-Perdew-Burke-Ernzerhof (GGA-PBE) as well as modified Beck-Johnson correction (mBJ-GGA) approaches. The outcomes showed that both materials were optimal in the non-magnetic phase (NM). Minus value of computed formation energy advocates that these solids were energetically optimum and synthesized. The calculations of electronic characteristics of the investigated compounds exhibit typical semiconductor behaviour, with band gap energies of 0.639 eV for Ti2FeNiSb2 and 0.432 eV for Ti2Ni2InSb. Our study extended to calculate and predicate the optical characteristics of materials, including the complex function, optical conductivity, refractive index, absorption index, and reflectivity. Interestingly, two materials show the utmost values of figure-of-merit (ZT) and the Seebeck coefficient (S), computed by semi-local Boltzmann transport theory, indicating that these solids are appealing candidates and suitable for thermoelectric uses. Additionally, the quasi-harmonic model was performed to compute the thermo-dynamic characteristics; for instance, constant volume calorific capacity (CV), constant pressure calorific capacity (Cp), Debye temperature (D), thermal expansion coefficient (α) and entropy (S).