Ab initio study of phononic thermal conduction in ScAgC half-Heusler

In the last few years, a great deal of interest has centred on phonon studies in material science. Therefore, the present study consists of first-principles lattice calculations to comprehend the thermal expansion $$\alpha (T)$$ α ( T ) and lattice thermal conductivity $$\kappa _{ph}$$ κ ph of ScAgC. The obtained positive frequencies of phonon dispersion with and without non-analytic term correction (NAC) shows the dynamical stability of ScAgC in FCC structure. The estimated $$\alpha (T)$$ α ( T ) from quasi-harmonic approximation (QHA) at 300(1200) K is $$\sim $$ ∼ 4(4.6) $$\times $$ × $$10^{-6}$$ 10 - 6 K $$^{-1}$$ - 1 . The predicted value of total $$\kappa _{ph}$$ κ ph from phonon–phonon interaction (PPI) at 300(1200) K is $$\sim $$ ∼ 7.4(1.8) Wm $$^{-1}$$ - 1 K $$^{-1}$$ - 1 . The highest group velocity for acoustic and optical branches (AB and OB) is $$\sim $$ ∼ 6.7 and $$\sim $$ ∼ 3.5 km/s, respectively. The predicted average phonon lifetime ( $$\tau _{\lambda }$$ τ λ ) for AB(OB) is $$\sim $$ ∼ 2.5(1.65) ps at 300 K, whereas it is $$\sim $$ ∼ 0.6(0.4) ps at 1200 K. The estimated highest heat capacity ( $$C_{\lambda }$$ C λ ) at 200 K for AB(OB) is $$\sim $$ ∼ 23.5 (19.5) meV/K. We fitted the equation $$A_{\kappa }$$ A κ T $$^{-x_{\kappa }}$$ - x κ ( $$A_{\tau }$$ A τ T $$^{-x_{\tau }}$$ - x τ ) in the $$\kappa _{ph}$$ κ ph ( $$\tau _{\lambda }$$ τ λ ) curve to gain a thorough understanding of temperature-dependent $$\kappa _{ph}$$ κ ph trend. The $$x_{\tau }$$ x τ value due to total AB(OB) is estimated to be $$\sim $$ ∼ 1.04(1.02), while it is $$\sim $$ ∼ 1.03 for total branches. The $$x_{\kappa }$$ x κ for total branches is calculated to be $$\sim $$ ∼ 1.02, while it is $$\sim $$ ∼ 1.04(0.95) for total AB(OB) branches, implying that AB contributes more to the total $$\kappa _{ph}$$ κ ph . This research could be important for enhancing the properties of ScAgC regarding thermoelectric and photovoltaic applications.