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首页> 外文期刊>Physical review >Temperature-dependent multilayer relaxation of clean and hydrogen-dosed Nb(100)
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Temperature-dependent multilayer relaxation of clean and hydrogen-dosed Nb(100)

机译：清洁和氢掺杂Nb（100）的温度依赖性多层弛豫

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摘要

Low-energy-electron-diffraction intensity measurements and multiple scattering analysis are used to determine the multilayer surface relaxation of clean and hydrogen-dosed Nb(100) as a function of temperature. Accurate characterization of residual surface impurity concentration (oxygen) based on Auger electron spec-troscopy is used to obtain a meaningful extrapolation of the first-layer relaxation to the clean surface value: d_(12)=1.481± .05 A corresponding to △_(12)=-10±3%, a 10% relaxation relative to the bulk value d_0=1.645 A. This experimental result for d_(12) can be used to judge the accuracy of recent ab initio calculations for Nb(100). Temperature-dependent changes in surface relaxation resulting from hydrogen dosing of Nb(100) manifest an expansion of the near-surface lattice resulting from subsurface hydrogen atoms. The hydrogen-induced expansion of near-surface interplanar separation is determined to be 3±1% at T=125 K, 4±1% at T=300 K, and -1±1% at T=400 K. The measured hydrogen-induced surface lattice expansion is consistent with the bulk lattice constant change (△～ 4.5%) that occurs when Nb is hydrated to form βNbH. The observed relaxation of the hydrogen-dosed near-surface interplanar separation to the clean surface value for T > 400 K is consistent with the subsurface "hydrogen valve" model that has been used to account for unusual hydrogen uptake kinetics associated with Nb(100).
机译：低能量电子衍射强度测量和多次散射分析用于确定干净的和氢掺杂的Nb（100）随温度变化的多层表面弛豫。基于俄歇电子能谱的残留表面杂质浓度（氧气）的准确表征可用于获得第一层弛豫到干净表面值的有意义的推断：d_（12）= 1.481±.05 A对应于△_ （12）=-10±3％，相对于体积值d_0 = 1.645 A松弛10％。d_（12）的实验结果可用于判断Nb（100）的最近从头算的准确性。 Nb（100）的氢剂量引起的表面弛豫的温度依赖性变化表明，亚表面氢原子导致了近表面晶格的膨胀。氢引起的近表面平面间分离的膨胀在T = 125 K时为3±1％，在T = 300 K时为4±1％，在T = 400 K时为-1±1％。诱导的表面晶格膨胀与当Nb水合形成βNbH时发生的整体晶格常数变化（△〜4.5％）一致。对于T> 400 K，观察到的氢剂量近表面平面间距向清洁表面值的松弛与地下“氢气阀”模型一致，该模型已用于解释与Nb（100）相关的异常氢气吸收动力学。

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