Atomic Structure of the (310) Twin in Niobium: Theoretical Predictions and Comparison with Experimental Observation

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Abstract
High - resolution transmission electron microscopy (HREM) has been used to characterize the atomic structure of the symmetric 36.9° tilt grain boundary with [001] tilt axes forming a twin about (310) in Nb. The projected structure was imaged along two different directions in the plane of the boundary and was compared to model structures through high - resolution image simulation. The atomic structure of this Σ5 boundary was predicted with atomistic simulations using interatomic potentials derived from the Embedded Atom Method (EAM), Finnis-Sinclair (FS), and the Model Generalized Pseudopotential Theory (MGPT). The EAM and FS predicted structures with translations of the adjacent crystals which break mirror symmetry. The MGPT predicted one stable structure with mirror symmetry. The atomic structure of the (310) twin in Nb was found by HREM to be mirror symmetric. These findings indicate that the angular dependent interactions modeled in the MGPT are important for determining the grain boundary structures of bcc transition metals.