Comprehensive Investigation of Structural, Mechanical, Electronic, Phonon, Thermal, and Optical Properties of CrSnX (X = Pd, Pt) Half-Heusler Alloys: An Ab Initio Study

Abstract In this study, we conducted a comprehensive investigation of the structural, electronic, mechanical, and dynamical properties of CrSnPd and CrSnPt using density functional theory. The studied compounds exhibit negative formation energies, indicating thermodynamic stability and potential for successful synthesis under suitable experimental conditions. All investigated compounds satisfy the Born–Huang mechanical stability criteria, and phonon dispersion analyses confirm dynamical stability. Electronic band structure, density of states, and charge density analyses reveal metallic behavior, consistent with predominantly metallic bonding. Vibrational analysis shows ultralow lattice thermal conductivities ( $$\kappa _l$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>κ</mml:mi> <mml:mi>l</mml:mi> </mml:msub> </mml:math> ) of 0.208 W m $$^{-1}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:mmultiscripts> </mml:math> K $$^{-1}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:mmultiscripts> </mml:math> for CrSnPd and 0.298 W m $$^{-1}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:mmultiscripts> </mml:math> K $$^{-1}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:mmultiscripts> </mml:math> for CrSnPt at 300 K, supported by phonon group velocities, lifetimes, and strong lattice anharmonicity reflected in high Grüneisen parameters ( $$\gamma $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>γ</mml:mi> </mml:math> = 2.51−2.75). The calculated minimum thermal conductivities ( K $$_{min}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow> <mml:mi>min</mml:mi> </mml:mrow> <mml:mrow/> </mml:mmultiscripts> </mml:math> = 0.343−0.350 W m $$^{-1}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:mmultiscripts> </mml:math> K $$^{-1}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:mmultiscripts> </mml:math> ) provide a theoretical lower bound, confirming the reliability of the low $$\kappa _l$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>κ</mml:mi> <mml:mi>l</mml:mi> </mml:msub> </mml:math> values. Thermodynamic properties, including Gibbs free energy and heat capacity, indicate enhanced thermal stability and conductivity from CrSnPd to CrSnPt, with CrSnPt being more robust. Debye temperature analysis further supports stronger bonding in CrSnPt. The optical properties suggest that these materials are strong absorbers of ultraviolet radiation. All calculated optical parameters indicate a metallic nature, consistent with their electronic characteristics. Overall, these findings offer new insights into the stability, bonding, and transport properties of CrSnPd to CrSnPt intermetallics and provide a solid theoretical foundation for their experimental development and targeted applications in thermoelectrics, catalysis, and advanced functional materials.