VIBRATIONAL-MODES OF SILICON NANOSTRUCTURES

We present a method for predicting the vibrational modes of small semi conductor clusters. We employ ab initio pseudopotentials and apply a h igher-order finite difference procedure to solve the Kohn-Sham equatio ns. We predict the vibrational modes of small silicon clusters (Si-n, n = 4-7) based on their ground state structures. Our calculated vibrat ional modes agree very well with experimental data, and with other the oretical calculations based on quantum chemistry and tight binding met hods. This comparison confirms the accuracy of the finite difference p rocedure for calculating not only the first order derivative of the en ergy, but the second derivatives as well. It also validates the accura cy of pseudopotential-local density calculations for the ground state structures for Si clusters.