Stability of small Ni－Ti bimetallic clusters studied by density functional theory

The low-energy structures and the electronic and the magnetic properties of small Ni_nTi_n (n=1--6) and Ni_mTi_n (1 \le n \le 4, 1 \le m \le 4, n \ne m) clusters are investigated by performing all-electron calculations based on density functional theory. Ground states and several isomers near the ground states are determined for these clusters. The results indicate that the growth of small Ni_mTi_n clusters prefers to form rich Ti--Ni and Ti--Ti bonds. When the percentage of titanium atoms is significantly greater than that of nickel atoms, the nickel atoms are most frequently found above the surface; in contrast, the titanium atoms prefer the bridging sites. A M\"ulliken spin population analysis indicates that the total spin of titanium-nickel clusters is not always zero.