shows the correlation between (λphase /aFF) and the 95% confidence interval of the predicted interphase thickness after 500 iterations. As discussed before, the error increases drastically when (λphase /aFF) < 3, thus providing a good criterion for the lower limit of interphase thickness that can be detected. We argue that (λphase /aFF) ≈ 3 is sufficiently large to safely apply our sigmoid fitting approach and we suggest that 3aFF provides a robust criterion for our quantitative interphase thickness determination. confidence interval of the predicted interphase thickness. The gray box shows the area of (λphase/aFF) < 3 ,where our sigmoidal fitting approach fails.