Bonding Character and Formation Energy of Point Defects of He and Vacancy on (001) Surface of bcc Iron by First Principle Calculations

doi:10.1007/s40195-011-0504-z

Abstract

Abstract:

The structure and energy of He impurities and vacancy on (001) surface of bcc iron are investigated by an ab initio method. Three cases for stabilities of a He atom at the surface are found: some of He atoms at surface atomic layers (SAL) relax into vacuum gap; some of surface He atoms at octahedral interstitial site relax into more stable tetrahedral interstitial site; some of surface He atoms still stay at tetrahedral interstitial site. The un-stability of the He atom at the surface system can be explained by deformation mechanism of charge densities and electronic densities of states. It is found that formation energy of the point defects from the topmost SAL to bulk-like atomic layer increase gradually, for example, the formation energies of a monovacancy at the first five topmost SALs are equal to 0.33, 1.56, 2.04, 2.02 and 2.11 eV, respectively. The magnetic moments of Fe atoms in the surface atomic layers are also calculated.

Key words: ab initio calculations, Single point defects, bcc Fe (001) surface, Electronic structure

Jun CAI, Daogang LU. Bonding Character and Formation Energy of Point Defects of He and Vacancy on (001) Surface of bcc Iron by First Principle Calculations[J]. Acta Metallurgica Sinica (English Letters), 2013, 26(1): 25-32.

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