Origin of “Inverse Isotope Effect” of Hydrogen Diffusion in Palladium
Origin of “Inverse Isotope Effect” of Hydrogen Diffusion in Palladium
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氢在钯中扩散的“逆同位素效应”的起源
DOI：
10.4028/www.scientific.net/ddf.312-315.295
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
O. Yoshinari
中科院分区：
文献类型：
--
作者：
O. Yoshinari
在量子力学的框架下，确定了钯中氢(H)和氘(D)的扩散系数。用第一性原理计算得到的三维位能求解Schrödinger方程，确定了稳定的八面体(o)位和亚稳定的四面体(t)位的H和D的三维波函数和特征能。利用微推弹性带法得到的瞬态电位，确定了H和D沿扩散路径的态。沿扩散路径的特征能量曲线计算了隧穿矩阵元素(J)的大小。在Pd-H体系中，热激活的隧穿跃迁是主要的跃迁过程。另一方面，在Pd-D系统中，揭示了波函数扩散到o和t位点的扩展状态的过渡也对扩散有相当大的贡献。计算得到的H和D的扩散系数与实验值定量一致，再现了所谓的逆同位素效应。
The diffusion coefficients of hydrogen (H) and deuterium (D) in Pd were determined in the frame of a quantum mechanical consideration. The three dimensional (3D) wave functions and eigenenergies of H and D at a stable octahedral (o) site and a metastable tetrahedral (t) site were determined by solving the Schrödinger equation with 3D potentials obtained by the first principles calculation. The states of H and D along the diffusion path were also determined by using transient potentials which were obtained with an aid of the nudged elastic band method. The magnitudes of tunneling matrix elements (J) were evaluated from the eigenenergy curves along the diffusion path. In the Pd-H system, thermally activated tunneling transitions are dominant jump processes. On the other hand, in the Pd-D system, it is revealed that a transition via an extended state where the wave function spreads both to o- and t-sites also has a considerable contribution to the diffusion. The calculated diffusion coefficients for H and D quantitatively agreed with experimental values and the so-called inverse isotope effect was reproduced.