Possible lowest-energy geometry of silicon clusters Si(sub 21) and Si(sub 25)

A new approach that combines molecular mechanics/quantum mechanics procedure is presented, which can be used for determining the lowest energy-geometry for certain mid-sized silicon clusters like Si(sub 21) and Si(sub 25). Results indicate that the Si(sub 21) and Si(sub 25) are lower in energy and have a spherical-like structure.