Computer Simulation Of Point Defects In FCC Metals

Point defect is the most fundamental but the most important one of crystal defects, existing at a certain concentration in all materials. Point defect results in the increase of the material electrical resistivity, crystal volume and thermal expansion coefficient, and it also affects the mechanical properties of material by reciprocities with dislocation. In addition, diffusion of point defect is the dominant mechanism of atomic transport or diffusion in metals. Therefore, the studying of point defect in crystal is a central problem of materials, metallurgy, solid physics and even solid chemistry at all times. The people expect to improve the performance of materials or to provide a direction of theory for material designs by the speciality of point defect. In this paper, the formation energy and the migration energy for point defect in bulk, the uppermost layer of surface, and the layers near the surface of face centered cubic (FCC) metals are calculated with modified analytical embedded atom method (MAEAM) combining computer simulation. From the energy minimization, the stable configuration of di-vacancy, the favorable diffusion mechanism of the vacancy or the adatorn on the uppermost layer of surface, and the effects to the adsorption of the vacancy in a layer near the surface are discussed in detail. The results are shown in the following.(1) For the vacancy in the bulk of Cu crystal, FN di-vacancy is the most stable and likely occurs in practice in the three di-vacancy configurations. The preferred migration mechanism of the FN di-vacancy in Cu crystal is multi-jump of either vacancy (rotation the di-vacancy) rather than one jump of two vacancies so that the migration energy corresponding former is defined as the migration energy of di-vacancy.(2) For a vacancy or an adatom in the uppermost layer of surface in noble metals, the formation energy of a vacancy or an adatom increase with increasing atom density in the sequence (110)→(100)→(111), and it is difficult to form an adatom than to form a vacancy at the same surface. For the mobility of a vacancy, the migration energy grows in the sequence (100)→(110)→(111) for each noble metals, which is different from the sequence of the vacancy formation energy. The different ascribes the effect not only of the surface atom density, but also of the atoms below the surface in...