Megchiche E H, Amarouche M, Mijoule C
Laboratoire de Physique Quantique, IRSAMC (UMR 5626), Université Paul Sabatier, 118 route de Narbonne, 31062, Toulouse Cedex 4, France. Laboratoire de Physique et Chimie Quantique (LPCQ), Université Mouloud Mammeri, Tizi-Ouzou, Algeria.
J Phys Condens Matter. 2007 Jul 25;19(29):296201. doi: 10.1088/0953-8984/19/29/296201. Epub 2007 Jul 5.
Within the framework of density functional theory using the projector augmented-wave (PAW) method, we present some energetic properties of atomic oxygen interstitials in crystalline Ni, i.e. the insertion and activation energies of the O diffusion. Concerning the activation energy, two pathways for the migration process are studied. The charge transfer process between atomic oxygen and nickel atoms is analysed in the interstitial sites. We find that the interstitial octahedral site (O site) is lower in energy than the tetrahedral site (T site). The most favourable pathway for the migration between two octahedral sites corresponds to an intermediate metastable state located in a tetrahedral site. Concerning the charge transfers we find that the atomic oxygen ionizes as O(-) and that the electron migrates essentially from the Ni nearest neighbours of atomic oxygen. In addition, the thermal expansion contribution through the dilatation of the solid is studied. When the thermal expansion is introduced, we show that the insertion process is stabilized and that the tetrahedral insertion energy becomes nearly equal to the octahedral ones. However, the activation energy decreases with the dilatation. Taking into account the thermal expansion effects, our results are consistent with the more reliable experimental data.
在采用投影增强波（PAW）方法的密度泛函理论框架内，我们给出了晶体镍中原子氧间隙的一些能量性质，即氧扩散的插入能和活化能。关于活化能，研究了迁移过程的两条路径。分析了间隙位置处原子氧与镍原子之间的电荷转移过程。我们发现间隙八面体位置（O位置）的能量低于四面体位置（T位置）。两个八面体位置之间迁移的最有利路径对应于位于四面体位置的中间亚稳态。关于电荷转移，我们发现原子氧电离为O(-)，并且电子主要从原子氧的镍最近邻迁移。此外，研究了通过固体膨胀产生的热膨胀贡献。当引入热膨胀时，我们表明插入过程得以稳定，并且四面体插入能变得几乎等于八面体插入能。然而，活化能随膨胀而降低。考虑到热膨胀效应，我们的结果与更可靠的实验数据一致。
