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Extended point defects in crystalline materials: Ge and Si

This paper resolves a decades-long discussion over the nature of point defects - entities which enable mass transport in crystalline materials. A novel delocalised form - an amorphous-like pocket, or 'morph' - is shown to dominate self-interstitial diffusion in Ge at high temperature. The morph concept applies generally to the wide range of materials, from silicon to ice, which have a small amorphous-crystalline energy gap. Atomistic simulations illustrate the unexpectedly complex structures involved, underlining the importance of disorder in diffusion at high temperature. Preprint cited in major review (Mirabella, J. Appl. Phys., Jan2013), led to invited talk (GADEST 2013).