Density functional study on the bimetallic Ti_mZr_n (n + m ≤ 5) clusters and their interactions with H₂

Equilibrium geometries, stabilities, and electronic properties of small Ti_mZr_n (n + m ≤ 5) clusters were investigated using the density functional method. The ground states were determined, and it was found that the larger clusters and those consisting of more Zr atoms are more stable. The electronic properties of the clusters were discussed based on HOMO–LUMO gaps, vertical ionization potentials (VIP), and vertical electron affinities (VEA). Furthermore, we studied the interactions between those clusters and molecular hydrogen, and found that in all the cases dissociative chemisorptions occurred. According to the chemisorption energies, the pure Zr clusters are relatively more active towards H₂ when compared with the others except Ti₃Zr, which shows the highest activity. The magnetic moments of Ti_mZr_n and Ti_mZr_n H ₂ were also compared, and the results show that the hydrogenated clusters have the same or decreased total magnetic moments with respect to the bare clusters except for Ti₃Zr₂. (paper)