Precipitation pattern formation

摘要

Precipitation patterns have been observed in initially uniform salt solutions. They cannot be explained by Ostwaldrsquo;s supersaturation mechanism, which requires concentration gradients. A theory of them is presented based on the Cahnndash;Hillard equation for the salt concentrationc. It shows that there is a range of initial concentrations which give rise to periodic precipitation patterns provided that the diffusion coefficientD(c) is negative for some range ofc.