New structural configurations and novel diffusion mechanisms were proposed for neutral di-As interstitial (As2I2) in Si using a first-principles density functional theory simulation within the generalized gradient approximation. With an assumption of excess Si interstitials and high As concentrations, neutral As2I2 was expected to be favorable and mobile, with low migration-barrier. Moreover, because the diffusion barrier of As interstitial pairs (AsI) was very low (< 0.2eV) under the same conditions, As2I2 could be easily formed and be the likely intermediate stage of larger As interstitial clusters.

First-Principles Studies of Di-Arsenic Interstitial and its Implications for Arsenic-Interstitial Diffusion in Crystalline Silicon. Y.Kim, T.A.Kirichenko, N.Kong, L.Larson, S.K.Banerjee: Physica B, 2007, 401-402, 144-7