Basic Structural Units of Tilt Grain Boundaries. Part I. Misorientation Axis [100]

The computer simulation methods have been applied to calculate structure and energy of symmetric tilt grain boundaries with the misorientation axis [100]. The calculations have been carried out with the use of the structural-vacancy model previously developed by the authors. The misorientation angles of grain boundaries of common type have varied from 0° up to 90° while the increment has amounted 1°. The the reciprocal density of the coincidence sites in special grain boundaries has amounted Σ ≤ 53. The calculations have been carried out with the use of the Morse pair potential and the Cleri–Rosato many-body potential. It is shown that the dependence of the energy of grain boundaries on the misorientation angle when calculated with different potentials has a similar form, and their structure does not depend on the choice of potential and is in good agreement with high-resolution electron microscopic images. Only one special grain boundary is distinguished on the energy curve which is Σ5(013). It has been found that the structure grain boundaries may be represented by a limited number of atomic groups that have been named basic structural units. The structure of low-angle grain boundaries with the misorientation angle less than 8° is described by alternation of basic structural units of D types and ideal crystal, while the structure of low-angle grain boundaries with the misorientation angle ranging from 8° up to 13° is described by alternation of structural units of C and D types, from 14° up to 23° – B and C types. High-angle grain boundaries in the range of misorientation angles from 24° up to 37° contain only of basic structural units of B types, from 38° to 50° – A and B, more than 50° – only A.