The Ring cum Vacancy Mechanism of Diffusion in Pure Metals

The experimentally determined self diffusion coefficient of copper has been found to deviate from that predicted by vacancy mechanism at lower temperatures (below 900 Celsius). Such behaviour is not unexpected since vacancy concentration in metals rapidly decreases with decreasing temperature following an exponential relationship. This means that the vacancy mechanism cannot be the principal driving mechanism for self diffusion copper and there must be an alternative mechanism occurring at those temperatures. This paper explores the possibility of that alternative mechanism with the help of the mathematical model validated against the experimental diffusivity data at the experimental temperatures. With this validation it is found that a mixed diffusion mechanism which is a conjoint of two different mechanisms (vacancy and ring diffusion mechanism) can be that alternative mechanism driving the self-diffusion in copper at lower temperatures