We have studied, by the ab initio Car-Parrinello molecular-dynamics approach, the structure and band gaps of III-V semiconductor clusters included in sodalite as a function of the cluster size up to full filling of the sodalite cage. This study allows us to address directly the role of quantum confinement. The minimum-energy structures present large deviations from bulklike tetrahedral coordination and are reminiscent of amorphous structures. In contrast to the quantum confinement picture, the energy gap grows for increasing cluster size. The shift of the gap is instead due to an effective tensile/compressive strain exerted by the cage on the cluster and is comparable to the variation of the bulk band gap under the effect of hydrostatic pressure.

• Received 16 March 1999

DOI:https://doi.org/10.1103/PhysRevB.60.6131