AbstractThe structures and energies of a series of symmetrical 〈011〉 tilt grain boundaries in silicon are calculated for the first time using the tight‐binding type electronic theory (the bond orbital model). The boundary energies are highly dependent on the types and arrangements of the structural units which consist of 5‐, 6‐, 7‐, and 8‐membered rings of atoms. The boundary structures in the range 0° ≦ 0 ≦ 70.53° are analyzed in detail by the structural unit model, and it is shown that the comparatively simple structures of special boundaries, such as the Σ = 9 (122) boundary, a