面心立方镧中空位浓度随温度变化的阿克里尼乌斯定律的失效
Breakdown of the Arrhenius Law of the Temperature Dependent Vacancy Concentration in fcc-Lanthanum
摘要：
我们用原位正电子湮没谱测量了与温度有关的平衡空位浓度，以确定在元素fcc-La中空位形成的焓$H_\text{f}$和熵$S_\text{f}$。然而，应用于数据分析的阿克里尼乌斯定律未能解释$S_\text{f}$和$H_\text{f}$的意外高值：特别是与其他元素金属相比，$S_\text{f}=17(2)~k_\text{B}$大一个数量级，并且发现$H_\text{f}$的实验值与理论值$H_\text{f}=1.46~\text{eV}$（我们在$T=0~\text{K}$下对La的\acs{dft}计算）相差三个标准差以上。给出了一个一致的解释，超越了经典的阿克里乌斯方法的空位形成熵的温度依赖性与$S_\text{f}^\prime=-0.0120(14)~k_\text{B}/\text{K}$占空位引入的非谐势。
英文摘要：
We measured the temperature dependent equilibrium vacancy concentration using in-situ positron annihilation spectroscopy in order to determine the enthalpy $H_\text{f}$ and entropy $S_\text{f}$ of vacancy formation in elementary fcc-La. The Arrhenius law applied for the data analysis, however, is shown to fail in explaining the unexpected high values for both $S_\text{f}$ and $H_\text{f}$: in particular $S_\text{f}=17(2)~k_\text{B}$ is one order of magnitude larger compared to other elemental metals, and the experimental value of $H_\text{f}$ is found to be more than three standard deviations off the theoretical one $H_\text{f}=1.46~\text{eV}$ (our \acs{dft} calculation for La at $T=0~\text{K}$). A consistent explanation is given beyond the classical Arrhenius approach in terms of a temperature dependence of the vacancy formation entropy with $S_\text{f}^\prime=-0.0120(14)~k_\text{B}/\text{K}$ accounting for the anharmonic potential introduced by vacancies.
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