Phase stability and mechanical response of the ordered ScTaCo₂Sb₂ crystal: insights from first-principles...

This study presents a systematic first-principles investigation of the lattice stability, mechanical properties, electronic structure, and lattice thermal conductivity of the Double Half-Heusler compound ScTaCo₂Sb₂. The phonon spectrum shows no imaginary frequencies, confirming its lattice dynamic stability. The electronic structure reveals it to be a direct-bandgap semiconductor with a pressure-tunable bandgap. Mechanical calculations confirm that the material satisfies the mechanical stability criteria and exhibits near-critical ductile-to-brittle characteristics. The calculated lattice thermal conductivity is 1.04 W m^-1 K^-1, which satisfies the low thermal conductivity requirement for high-efficiency thermoelectric materials. These results demonstrate that ScTaCo₂Sb₂ possesses both excellent mechanical stability and low lattice thermal conductivity, positioning it as a promising candidate for thermoelectric applications. While previous work focused on the electronic structure and optical properties of this compound, the present study uniquely addresses its mechanical stability, elastic moduli, ductile-to-brittle transition behaviour, and lattice thermal conductivity, providing essential insights for its potential thermoelectric applications. This work provides a theoretical foundation for the application and materials design of Double Half-Heusler alloys in the field of thermoelectrics.