First-principles calculations for the vibrational frequencies H-2 and H-2* complexes in Si

Abstract

We present the results of first-principles pseudopotential calculations for the local vibrational frequencies of H-2 and H-2* complexes in crystalline Si within the local-density-functional approximation. The vibrational modes and frequencies are determined by the full, dynamical matrix which is constructed using a supercell geometry. Including gradient corrections for the exchange-correlation potential, we find the vibrational frequencies of 2071 and 1784 cm(-1) for the stretch modes of the H-2* complex, while 784 and 598 cm(-1) for the wagging modes, consistent with experimentally measured values. For the H-2 molecule at a tetrahedral site, we examine the [100], [110], and [111] orientations, and find the stretch modes in the range of 3556 similar to 3643 cm(-1), in good agreement with previous calculations and experiments.