High-accuracy Monte Carlo simulations were made of vacancy and tracer diffusion in a random A-B body-centered cubic alloy. The vacancy and tracer correlation factors were calculated by using the Einstein equation, and the mean square displacements in the absence of driving forces. Also, the vacancy correlation factor was calculated from the vacancy drift in the presence of a driving force. The results were compared with the predictions of the Manning random alloy model. Good agreement was found only with regard to the vacancy correlation factor, and the atomic correlation factors in the impurity limits. It was found that, within the range of concentrated alloys, the Manning model markedly over-estimated the atomic correlation factors; even for relatively small A/B exchange frequency ratios; such as 5. The percolation threshold, and the critical exponents, were found to be reasonably consistent with the results of other Monte Carlo simulations. Comparison with the Monte Carlo results demonstrated that the basic relationships of the Manning model were not strictly obeyed in concentrated alloys.

Y.Mishin, D.Farkas: Philosophical Magazine A, 1997, 75[1], 201-19