Quantitative Interpretation of Isotope Correlation Coefficient Ratios in Solid Diffusion

The correlation coefficient f is crucial in the calculation of the absolute diffusion coefficient D, especially for the vacancy mechanism. The current study for f is complex and contains many approximations and assumptions. However, f can be ignored when considering the isotope effect, which has only been stated qualitatively by previous authors and not explained from a quantitative perspective. In this paper, we will explain the reason why f can be neglected in the isotope diffusion effect by finding the most essential formula and source of f, as a way to save the most troublesome step in the calculation of the isotope diffusion effect.