Ternary Diffusion: Restrictions on the (2D) Matrix

An analysis has been made of ternary diffusing systems to determine the possibility that individual diagonal interdiffusion coefficient elements of the_k(²D) (k = 1,2,3) interdiffusion coefficient matrices can be negative. It is shown that in ternary diffusing systems, in which the concentration-penetration curves are monotonic, as many as three of the six diagonal coefficients can be negative. It is further shown that several ternary diffusing systems having a negative diagonal interdiffusion coefficient matrix element have already in fact been determined experimentally.