Entropic measure of spatial disorder for systems of finite-sized objects

We consider the relative configurational entropy per cell S-Delta as a meas ure of the degree of spatial disorder for systems of finite-sized objects. It is highly sensitive to deviations from the most spatially ordered refere nce configuration of the objects. When applied to a given binary image it p rovides the quantitatively correct results in comparison to its point objec t version. On examples of simple cluster configurations, two-dimensional Si erpinski carpets and population of interacting particles, the behaviour of S-Delta is compared with the normalized information entropy H' introduced b y Van Siclen [Phys. Rev. E 56 (1997) 5211]. For the latter example, the add itional middle-scale features revealed by our measure may indicate for the traces of self-similar structure of the weakly ramified clusters. In the th ermodynamic limit, the formula for S-Delta is also given. (C) 2000 Elsevier Science B.V. All rights reserved.