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Symmetrical tilt grain boundaries in bcc transition metals: comparison of semiempirical with ab-initio total-energy calculations
Five different semiempirical total-energy methods, provided in the literature and applicable for atomistic simulations of extended defects in bce transition metals, are investigated in a comparative study. The comparison is made with recent theoretical ab-initio (local-density-functional theory) and experimental (high-resolution transmission electron microscopy) studies for the specific case of the Sigma = 5, (310) symmetrical tilt grain boundaries (Sigma = 5 STGBs) in Nb and Mo. The considered semiempirical real-space approaches based on different approximations of the tight-binding and related methods are the Finnis-Sinclair central-force potentials, non-central-force bond-order potentials recently advanced by Pettifor and co-workers, and non-central-force potentials based on the model-generalized pseudopotential theory of Moriarty. As semiempirical reciprocal-space methods, a very simple d-basis tight-binding model by Paxton and an elaborate environment dependent spd-basis orthogonal tight-binding model by Haas ct al. are included in the analysis. The virtues and deficiencies of these models in their ability to predict the translation states and interfacial energies of the Sigma = 5 STGB are discussed.