First-Principles Investigation of Structural, Electronic, Phonon and Thermoelectric Properties of Ir2YSi (Y = Be, Ca and Sr) Heusler

Abstract

This work presents a first-principles study of the structural, mechanical, dynamical, electronic, and thermoelectric properties of the ternary Heusler compounds Ir 2 YSi (Y = Be, Ca, Sr). These materials crystallize in the cubic L2 1 structure (space group [Formula: see text]) and are found to be thermodynamically stable, with the non-magnetic state being energetically favored. The calculated elastic constants satisfy the Born criteria, confirming mechanical stability for all compounds, although Ir 2 SrSi shows relatively lower rigidity. Phonon dispersion curves exhibit no imaginary frequencies, indicating dynamical stability, with vibrational properties influenced by atomic mass differences. Electronic structure analysis reveals a metallic character for all compounds, with dominant Ir-[Formula: see text] states near the Fermi level and notable hybridization with Si-[Formula: see text] orbitals. A pseudo-gap observed in Ir 2 CaSi and Ir 2 SrSi suggests enhanced stability compared to Ir 2 BeSi. Thermoelectric properties show metallic behavior with increasing electrical and thermal conductivities as temperature rises. Despite some improvement across the series, the maximum figure of merit remains low ([Formula: see text]), limiting their efficiency for thermoelectric applications.