Vacancy mechanism of the anomalous behavior of surface atoms at elevated temperatures

A model that takes into account the significant contribution of vacancies a t moderate and high temperatures is proposed to explain the anomalous incre ase in the mean-square displacements of atoms in transition-metal surface m onolayers. The dependence of the effects on the orientation of the surface is explained. The vacancy formation energies and the values of the Debye te mperature are obtained within the proposed model for differently oriented s urfaces. (C) 1999 American Institute of Physics. [S1063-7761(99)01212-3].