Abstract
Equilibrium morphologies of three types of cesium halide crystals in
saturated aqueous solution droplets are observed for temperatures ranging
from 275 to 344 K. For all temperatures, cesium iodide crystallites are
bounded by planar {1 1 0} facets, which indicates that these faces are
below the roughening temperature. On the other hand, cesium chloride surfaces
are thermally roughened in this temperature regime, as follows from their
rounded morphology. For cesium bromide a roughening transition is observed
at a temperature of 278±1 K. This value of the roughening temperature
allows us to estimate the effective bond energy at the surface of this
ionic compound. The abruptness of the transition, which takes place within
2 K, suggests that probably it is not of the Kosterlitz–Thouless type.