Stability of vacancy-hydrogen clusters in nickel from first-principles calculations
Stability of vacancy-hydrogen clusters in nickel from first-principles calculations
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DOI：
10.1016/j.actamat.2014.06.021
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发表时间：
2014-10
期刊：
影响因子：
9.4
通讯作者：
D. Tanguy;Yu Wang;D. Connétable
中科院分区：
文献类型：
--
作者：
D. Tanguy;Yu Wang;D. Connétable
用从头计算方法研究了氢原子与空位的相互作用。单空位和双空位的最低分凝能分别为-0.27和-0.41 eV。这些值与对应于热脱附光谱的两个特征峰的那些值非常一致。实验数据的微观解释，因此澄清。从从头算数据出发建立了一个能量模型，并用于研究氢体浓度和温度对空位氢团簇浓度的影响。给出了解析表达式，并通过蒙特卡罗模拟进行了验证。平均空位占用和H-引起的空位富集计算在两个温度下的H脆化实验和应力腐蚀开裂在高温下的代表。VH 6簇的稳定域被发现显着重叠的实验条件脆化。因此，在高浓度的空位聚集可以定性地讨论的基础上VH 6-VH 6的相互作用，发现弱排斥。H损伤在Ni的后果进行了讨论。金属振动对偏析和局部氢化物稳定性的影响是定性评估的非晶格蒙特卡罗模拟使用半经验的Ni-H势。他们被证明是转向本地氢化物的稳定性向更高的H浓度。
The interactions of hydrogen (H) atoms with vacancies are investigated by means of ab initio calculations. The lowest segregation energies are− 0.27 and− 0.41 eV at single vacancies and divacancies, respectively. These values are in excellent agreement with those corresponding to the two characteristic peaks of the thermal desorption spectra. The microscopic interpretation of the experimental data is therefore clarified. An energetic model is built from the ab initio data and used to study the influence of H bulk concentration and temperature on the concentration of vacancy-H clusters. Analytical expressions, validated by Monte Carlo simulations, are given. The mean vacancy occupation and the H-induced vacancy enrichment are calculated at two temperatures representative of H embrittlement experiments and stress corrosion cracking at high temperatures. The stability domain of VH 6 clusters is found to significantly overlap with the experimental conditions for embrittlement. Therefore, vacancy clustering at high concentrations can be qualitatively discussed based on VH 6–VH 6 interactions that are found weakly repulsive. Consequences on H damage in Ni are discussed. The effect of metal vibrations on segregation and local hydride stability is qualitatively evaluated by off-lattice Monte Carlo simulations using a semi-empirical Ni–H potential. They are shown to shift local hydride stability towards higher H concentrations.