Volume-term theories of phase separation in colloidal systems and long-range attractive tail in the pair potential...

To explain the experimental observation that colloidal dispersion exhibits a "two-state" structure under certain conditions, Sogami and Ise (SI) proposed a model for an "effective" pair potential between colloidal particles which had an "attractive tail" more than a decade ago. The SI paper spawned several papers that dwelled on the shortcoming of the SI paper or strived to provide other explanations for the observed inhomogeneity of the suspension. We show herein that a long range attraction in the pair potential between colloidal particles is also obtained in "volume-term" theories in which the repulsive DLVO potential is retained.