ScAgC半赫斯勒合金中声子热传导的从头算研究
Ab-initio study of phononic thermal conduction in ScAgC half-Heusler
AI总结：
该研究通过第一性原理计算ScAgC半赫斯勒合金的热膨胀和晶格热导率，发现其动力学稳定，声学支对热导率贡献更大，对热电和光伏应用有潜在价值。
摘要：
我们提出了第一性原理晶格计算，以理解ScAgC的热膨胀α(T)和晶格热导率κ_ph。获得的声子色散的正频率表明ScAgC在FCC结构中具有动力学稳定性。在300(1200) K下，通过准谐近似(QHA)估算的α(T)约为4(4.6)×10⁻⁶ K⁻¹。在300(1200) K下，由声子-声子相互作用(PPI)预测的总κ_ph值约为7.4(1.8) Wm⁻¹K⁻¹。声学支(AB)和光学支(OB)的最高群速度分别约为6.7和3.5 km/s。在300 K时，AB(OB)的平均声子寿命(τ_λ)预测约为2.5(1.65) ps，而在1200 K时约为0.6(0.4) ps。在200 K时，AB(OB)的最高热容(C_λ)估算约为23.5(19.5) meV/K。我们在κ_ph(τ_λ)曲线中拟合了方程A_κT⁻ˣ_κ(A_τT⁻ˣ_τ)，以深入理解温度依赖的κ_ph趋势。总支的x_κ计算约为1.02。由于总AB(OB)导致的x_τ值估算约为1.04(1.02)，而总支的x_τ约为1.03。计算得到的总AB(OB)的x_κ约为1.04(0.95)，表明AB对总κ_ph的贡献更大。这项研究对于提升ScAgC在热电和光伏应用中的性能可能具有重要意义。
英文摘要：
We present a first-principles lattice calculations to comprehend the thermal expansion $α(T)$ and lattice thermal conductivity $κ_{ph}$ of ScAgC. The obtained positive frequencies of phonon dispersion shows the dynamical stability of ScAgC in FCC structure. The estimated $α(T)$ from quasi-harmonic approximation (QHA) at 300(1200) K is $\sim$4(4.6)$\times$$10^{-6}$ K$^{-1}$. The predicted value of total $κ_{ph}$ from phonon-phonon interaction (PPI) at 300(1200) K is $\sim$7.4(1.8) Wm$^{-1}$K$^{-1}$. The highest group velocity for acoustic $\&$ optical branches (AB $\&$ OB) is $\sim$6.7 and $\sim$3.5 km/s, respectively. The predicted average phonon lifetime ($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_λ$) at 200 K for AB(OB) is $\sim$23.5 (19.5) meV/K. We fitted the equation $A_κ$T$^{-x_κ}$($A_τ$T$^{-x_τ}$) in the $κ_{ph}$($τ_λ$) curve to gain a thorough understanding of temperature-dependent $κ_{ph}$ trend. The $x_κ$ for total branches is calculated to be $\sim$1.02. The $x_τ$ 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 calculated $x_κ$ for total AB(OB) is $\sim$1.04(0.95), implying that AB contributes more to the total $κ_{ph}$. This research could be important for enhancing the properties of ScAgC regarding thermoelectric and photovoltaic applications.
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