Site occupancy of alloying elements in TiNi compounds

Abstract

A method is proposed on the basis of electronic structure calculations to predict the substitution behaviour of alloying elements in TiNi compounds. The electronic structures of 36 elements occupying both Ti and Ni sites in TiNi are calculated using the discrete variational-X _a cluster method. A diagram is drawn using Bo _Ti, and Bo _Ni, the total bond orders between the alloying elements and surrounding atoms. Two lines on the diagram separate the alloying elements into three groups. The elements located outside the two lines occupy either Ti or Ni sites regardless of the composition. The substitution behaviour of elements in between are affected by the alloy composition. The effects of composition, multielement alloying and ordering time and the influence of entropy are discussed. The results agree well with experiments.