RELAXATION AND STABILITY OF SMALL TRANSITION-METAL PARTICLES

The relaxation of interatomic distances in cubo-octahedral (fcc) and icosahedral Ni clusters of N atoms (13 ≤ N ≤ ∞) is determined by minimizing the cohesive energy. The electronic attractive term of the energy is calculated in the tight-binding approximation associated with the moments method, and the repulsive interaction between atoms is described by a Born-Mayer pair potential. One finds always a contraction, which is larger for the smaller clusters. The icosahedral structure is slightly favored for the small sizes, and the fcc structure becomes the most stable for clusters of more than 150 atoms. © 1979.