Rhodium based half-Heusler alloys as possible optoelectronic and thermoelectric materials

TL;DR

This study uses density functional theory to explore rhodium-based half-Heusler alloys, revealing their structural stability, semiconducting nature, optical properties, and potential for thermoelectric applications, especially RhTiBi with a high figure of merit.

Contribution

It provides a comprehensive theoretical analysis of rhodium-based half-Heusler alloys, highlighting their stability, electronic, optical, and thermoelectric properties, and identifies promising candidates for thermoelectric devices.

Findings

RhTiP is ductile; others are brittle.

Alloys are semiconducting with indirect band gaps 0.94-1.01 eV.

RhTiBi shows a figure of merit ~1, promising for thermoelectric use.

Abstract

On the basis of density functional theory and semi-classical Boltzmann theory, we have investigated the structural, elastic, electronic, optical and thermoelectric properties of 18--valence electron count rhodium based half-Heusler alloys focusing on RhTiP, RhTiAs, RhTiSb, and RhTiBi. The absence of imaginary frequencies in the phonon dispersion curve for these system verifies that they are structurally stable. RhTiP is ductile in nature, while others are brittle. The alloys are found to be semiconducting with indirect band gaps ranging from 0.94 to 1.01 eV. Our calculations suggest these materials to have high absorption coefficient and optical conductivity in the ultraviolet as well as visible region. While considering thermoelectricity, we found that $p$--type doping is more favorable in improving the thermoelectric properties. The calculated values of power factor with $p$-type doping are comparable to some of the reported half-Heusler materials. The optimum figure of merit \zt\ is $\sim1$ for RhTiBi suggesting it as a promising candidate for thermoelectric applications while RhTiP, RhTiAs, and RhTiSb with optimum \zt \ values between 0.38 to 0.67 are possible candidates for use in thermoelectric devices.