Stability, structural transformation, and reactivity of Ga-13 clusters

First-principles pseudopotential calculations were performed to investigate the atomic structure, structural transformation, and reactivity of Ga-13 c lusters. Ga-13 energetically favors a distorted decahedron. The decahedron is more stable than a relaxed icosahedron and a relaxed cuboctahedron by 0. 22 and 0.67 eV, respectively. Stuctural transformations from the cuboctahed ron and the icosahedron to the lowest-energy structure need to overcome bar rier heights of less than 0.55 and 0.05 eV, respectively. Small activation energies are responsible for the flexibility and floppiness of Ga-13 cluste rs. Reactions of the decahedral Ga-13 cluster with Ga and As atoms induce s tructural changes of the substrate and produce cohesive-energy gains of 3.6 5 and 4.71 eV, respectively. Migrations of the Ga and As adatoms on the sur face of the Ga,, cluster need to go over activation barriers with heights o f less than 0.30 and 0.34 eV, respectively.