Abstract: Based on grain boundary structural unit model, on the analogy of electric circuit calculation, it was found that the diffusion coefficients of a geneyal intervenient boundary between the delimiting boundaries 1 and 2 can be written as D_(11)=[D_((11)1) sin(φ_0-△θ/2)+D_((11)2)]/sinφ_0 D_⊥=D_(⊥1)D_(⊥2)sinφ_0/[sin (φ-△θ)D_(⊥2)+sin(△θ/2)D⊥1)] and D_(11)/D_⊥sin~2φ_0=D_((11)1)/D_(⊥1)sin~2(φ-△θ/2) +[(D_((11)2)/D_(⊥1))+(D_((11)1)/D_(⊥2)]sin(φ_0-△θ/2)sin(△θ/2) +(D((11)2)/D_(⊥2))sin~2(△θ/2) where D_(11) and D_⊥ are the diffusion coefficients pardllel to and perpendicular to the tilt axis, respectively. The subscripts 1 and 2 refer to the delimiting boundaries 1 and 2 respectively, and φ_0, the angle between periodic vectors of the strtictuyal units S_1 and S_2 which composes solely of delimiting boundaries 1 and 2 respectively. The experimental data from Hoffman, Upthegrove and Sinnot and Couling and Smoluchowski are analysed.

Key words: diffusion coefficient, grain boundary, dislocation pipe