  The microstructure of coagulated colloidal particles, for which the
inter-particle potential is described by the DLVO theory, is strongly
influenced by the particles' surface potential. Depending on its value, the
resulting microstructures are either more "homogeneous" or more
"heterogeneous", at equal volume fractions. An adequate quantification of a
structure's degree of heterogeneity (DOH) however does not yet exist. In this
work, methods to quantify and thus classify the DOH of microstructures are
investigated and compared. Three methods are evaluated using particle packings
generated by Brownian dynamics simulations: (1) the pore size distribution, (2)
the density fluctuation method and (3) the Voronoi volume distribution. Each
method provides a scalar measure, either via a parameter in a fit function or
an integral, which correlates with the heterogeneity of the microstructure and
which thus allows for the first time to quantitatively capture the DOH of a
granular material. An analysis of the differences in the density fluctuations
between two structures additionally allows for a detailed determination of the
length scale on which differences in heterogeneity are most pronounced.
