Y. Mishin et D. Farkas, MONTE-CARLO SIMULATION OF CORRELATION-EFFECTS IN A RANDOM BCC ALLOY, Philosophical magazine. A. Physics of condensed matter. Structure, defects and mechanical properties, 75(1), 1997, pp. 201-219
Results of high-accuracy Monte Carlo simulations of vacancy and tracer
diffusion in a random bcc alloy A-B are reported. The vacancy and tra
cer correlation factors are calculated using the Einstein equation and
the mean square displacements in the absence of driving forces. Addit
ionally, the vacancy correlation factor is calculated from the vacancy
drift in the presence of a driving force. The results are compared wi
th the predictions of Manning's random alloy model. Good agreement is
observed only for the vacancy correlation factor f(v), and the atomic
correlation factors f(A), and f(B) in the impurity limits. In the rang
e of concentrated alloys the Manning model markedly overestimates f(A)
and f(B) even for relatively small exchange frequency ratios such as
w(A)/w(B) = 5. The percolation behaviour of f(v) and f(A) when w(A) mu
ch greater than w(B) is analysed in detail. The percolation threshold
and the critical exponents are reasonably consistent with other Monte
Carlo simulations. By comparison with the Monte Carlo results we demon
strate that the basic relations of Manning's model (eqns. (10) and (12
)) are not strictly obeyed in concentrated alloys.