On the nature of the low energy of special twist grain boundaries

Abstract

The results of geometrical modeling of the structure of rigid twist grain boundaries with allowance for both full and partial coincidences of atomic sites in an FCC crystal that is considered as a close packing of spheres are presented. Values for the effective grain boundary energy depending on the misorientation angle for general-and special-type boundaries and on the reciprocal density of coincident sites for special-type boundaries have been obtained. It is shown that the low energy of special boundaries cannot be explained within the frame of the coincidence-site lattice (CSL) model, since it does not allow for partial coincidences. A nonmonotonic dependence of grain boundary energy on the reciprocal density of coincidence sites is obtained, which is confirmed experimentally.