The formation energy of monovacancy and binding energy of divacancy at and below the Mg (00•1) surface were examined by ab initio calculations based on the density-functional theory. Appropriate dense of k-point mesh and large super-cell was used to obtain reasonable values. During calculation, It was found that higher formation energy was needed to form monovacancy at the second layer. The electron density contour plots shows that electron tends to accumulate in the vicinity of vacancy at the second layer and accumulation charges were also impact on the stableness of the divacancies located at different layers. The migration barrier energy of transition state for the vacancy at the second layer was counted to be very low because of the accumulation electrons apply the power to make the vacancy to migrate. It was expected that the computational results would be useful for accounting for the diffusion of hydrogen atoms in the bulk of Mg and the mechanism of catalysis of impurities such as carbon for the diffusion of hydrogen atoms.

Do the Atoms at Second Layer Block the Path of Vacancies in the Bulk? – the DFT Study of Vacancies Below the Mg (0001) Surface. J.Guo, K.Huang, X.Zhao, H.Huang, Z.Yao: Physica Status Solidi B, 2010, 247[2], 259–64