A theoretical approach to the explanation of experimentally determined positive enthalpy of formation in Cr-based phases is presented. It turns out that the energy of formation of phases in Cr-Co and Cr-Fe systems is found to be negative taking the pure components in the -phase structure as the standard states. Our treatment represents a first step to a model of an explanation of the stability of the phase.

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Deformation properties of body-centered-cubic transition metals are controlled by the core structure of screw dislocations and their studies involve extensive computer simulations. In this paper we present the recently constructed bond-order potentials (BOP) that are based on the realspace parametrized tight-binding method. In order to examine the applicability of the potentials we have evaluated the energy differences of alternative structures, investigated several transformation paths leading to large distortions and calculated phonon dispersions. Using these potentials we have calculated γ-surfaces that relate to the dislocation core structures and discuss then the importance of directional bonding in studies of dislocations in transition metals.