Diffusion coefficient The diffusion coefficient D can be written as a temperature dependent part and independent part D0, i.e., D = D0 exp(-Q/RT). The D0 for interstitial C in FCC iron is 2.0 mm2 s-1. Estimate the vibration rate () of C, assuming no change in entropy of mixing due to hopping, i.e., Sm = 0. (Hint: you may need to google the lattice constant for FCC iron and based on this to compute the distance between to nearest interstitial sites in FCC iron).