Theoretical study on structural and electronic properties of Wn Nim (n plus m=8) clusters

The possible equilibrium geometries of W-n Ni-m (n + m = 8) clusters are optimized by using the density functional theory at the B3LYP/LANL2DZ level. For the ground state structures, the average binding energy, the wiberg bond index (WBI), the magnetism and the natural bond orbital (NBO) method are analyzed. The calculated results show that with the increase of the W atom number, the cluster becomes more stable. The strength in WBI is in the following order: W-W > W-Ni > Ni-Ni. When n >= 5, the W-n Ni-m (n + m = 8) clusters include the basic structure of W-n cluster. The magnetic moments of W-n Ni-m (n + m = 8) clusters are quenched at n = 5 and 6. Inside W and Ni atoms, the hybrid phenomenon happens, owing to the charge transfer. And the charge transfer also occurs between W and Ni atoms, thereby forming a strong chemical bond between W and Ni.