Fully quantum mechanical calculation of the diffusivity of hydrogen in iron using the tight-binding approximation and path integral theory
Fully quantum mechanical calculation of the diffusivity of hydrogen in iron using the tight-binding approximation and path integral theory
复制标题
使用紧束缚近似和路径积分理论全量子力学计算铁中氢的扩散率
DOI：
10.1103/physrevb.88.054107
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发表时间：
2013
影响因子：
3.7
通讯作者：
D. Pashov
中科院分区：
文献类型：
--
作者：
I. Katzarov;A. Paxton;D. Pashov
我们提出了氢在 bcc-Fe 中扩散的自由能垒和扩散率随温度变化的计算。这是一种完全量子力学方法，因为总能量景观是使用一种新的自洽、可转移的磁性铁中间隙杂质的紧密结合模型来计算的。此外，氢核也经过量子力学处理，我们在这里比较文献中的两种方法，两者都基于统计力学的费曼路径积分公式。我们发现，与基于自由能垒的固定质心计算的替代理论相比，允许质子探索相空间有更大自由的量子过渡态理论给出的结果与实验更好地一致。与最近的扩散率质心分子动力学（CMD）计算相比，我们还发现结果更加一致，该计算采用经典的原子间势而不是我们的量子力学紧束缚理论。特别是，我们首先发现量子效应持续到比之前想象的更高的温度，相反，低温扩散率小于 CMD 计算中的预测，大于经典过渡态理论的预测。这将对未来氢捕获和扩散的建模和模拟产生影响。
We present calculations of free energy barriers and diffusivities as functions of temperature for the diffusion of hydrogen in bcc-Fe. This is a fully quantum mechanical approach since the total energy landscape is computed using a new self consistent, transferable tight binding model for interstitial impurities in magnetic iron. Also the hydrogen nucleus is treated quantum mechanically and we compare here two approaches in the literature both based in the Feynman path integral formulation of statistical mechanics. We find that the quantum transition state theory which admits greater freedom for the proton to explore phase space gives result in better agreement with experiment than the alternative which is based on fixed centroid calculations of the free energy barrier. We also find results in better agreement compared to recent centroid molecular dynamics (CMD) calculations of the diffusivity which employed a classical interatomic potential rather than our quantum mechanical tight binding theory. In particular we find first that quantum effects persist to higher temperatures than previously thought, and conversely that the low temperature diffusivity is smaller than predicted in CMD calculations and larger than predicted by classical transition state theory. This will have impact on future modeling and simulation of hydrogen trapping and diffusion.