Surface atoms
What is the atoms' percentage on a solid's surface compared to its total volume?
Crystallite Size
This equation estimates the average crystallite size of a polycrystalline sample based on X-ray diffraction pattern
D = 0.9λ / bcosθ
References:
https://www.sciencedirect.com/topics/materials-science/scherrer-equation
https://www.nature.com/articles/nnano.2011.145
Volume Fraction
Estimation of volume fraction in spherical particle' solution