Segregation Driving Forces on the (111) and (110) Faces of a CuAg Alloy

Abstract

AbstractUsing a tight‐binding Isingmodel (TBIM), the segregation energy on the (111) face of a Cu‐Ag 0.45 at% alloy and on the (110) face of a Cu‐Ag 0.30 at% alloy as a function of surface coverage, is derived from equilibrium segregation experiments. It is shown that a surface size effect term which depends on the square of the surface concentration has to be introduced in the segregation energy of the (111) face in order to take into account the surface strain energy which occurs in the first layer when the silver atoms segregate at the surface. On the contrary, on the (110) face the segregation energy expression reveals that the surface size effect does not depend on the silver surface concentration. Also, the effective surface pair interaction βs can be determined and related to the effective bulk pair interaction βb through the relation βs = 1.37βb, for the (111) face and βs = 1.61βb for the (110) face, which is in good agreement with theoretical predictions.