Dispersion (materials science)
In materials science, dispersion is the fraction of atoms of a material exposed to the surface. In general, D = NS/N, where D is the dispersion, NS is the number of surface atoms and NT is the total number of atoms of the material.{{Citation|last=Bergeret|first=Gérard|title=Particle Size and Dispersion Measurements|date=2008|url=https://hal.archives-ouvertes.fr/hal-00308909/file/Bergeret2008.pdf|work=Handbook of Heterogeneous Catalysis|pages=738–765|publisher=American Chemical Society|language=en|doi=10.1002/9783527610044.hetcat0038|isbn=978-3-527-61004-4 |last2=Gallezot|first2=Pierre}} It is an important concept in heterogeneous catalysis, since only atoms exposed to the surface can affect catalytic surface reactions. Dispersion increases with decreasing crystallite size and approaches unity at a crystallite diameter of about 0.1 nm.