Abstract
We present the results of a parallel study of the atomic structure of the ∑ = 5, (210), θ = 53·13° and (310), θ = 36·87°, [001] tilt axis grain boundaries in bcc Mo, by computer simulation and high-resolution electron microscopy (HREM). Excess energy values of different boundary configurations are obtained via a quasidynamical minimization scheme while cohesion is described by a new n-body central-force, phenomenological potential which satisfactorily reproduces static and dynamical properties of the bulk material. HREM observations and numerical modelling both show the symmetric configuration of the ∑ = 5, (210), θ = 53·13° boundary to be of the lowest energy. The calculations also show that the stable ∑ = 5, (310), θ = 36·87° configuration is nearly mirror symmetric, although the experimental verification in this case is still incomplete. After a few oscillations, the interplanar spacing near the boundaries converges rapidly to its bulk value while producing an overall expansion of the bicrystal. Qualitative agreement is found between calculated and experimentally determined expansion values. The present results contradict the conclusions of earlier work according to which phenomenological n-body central-force potentials would not be able to provide a satisfactory description of the grain-boundary structure in bcc transition metals.