Features of Diffusion of Lead Atoms Embedded into a Defective Cu(111) Surface

Abstract

The results of calculations of energy barriers to the vacancy-mediated diffusion of Pb atoms embedded into the Cu(111) surface layer using quantum chemical density-functional theory are described. It is shown that the rate-limiting step of the migration of lead atoms is the degradation of the long-lived Pb–vacancy complex, not vacancy diffusion, as was observed for various impurity atoms on the Cu(100) face. The calculated energy barriers to the formation and degradation of this complex are 0.51 and 0.83 eV, respectively, while the barrier to monovacancy diffusion is 0.55 eV. The possibility of accelerating the diffusion of impurity Pb atoms at a high vacancy concentration owing to collisions of the Pb–vacancy complex with another vacancy is discussed.