Molecular Interpretation of Different Morphologies of KCl Microcrystals Growing From Aqueous Solutions

Abstract

Experimental data on the morphology of KCl microcrystals are interpreted from estimations of the possibility of growth of the (100) and (111)2 faces. Ion attachment energy and water adsorption energy for five different growth sites on the (100) face were calculated for different solution concentrations c and temperature T = 298.15 K using the molecular interaction model of cluster formation applied to large cubic KCl clusters with specified growth site in the centre of one of the (100) face. The results show that, above the equilibrium concentration c0 = 4.17 mol/dm3, attachment of ions is possible only for dislocation originated kink sites where the ion attachment energy is positive. For c > 5.3 mol/dm3, ions can also join a step producing new kink sites, thus increasing the growth velocity of (100) face. Further increase in the growth velocity is predicted to occur in solutions with c > 5.7 mol/dm3 when formation of growth islands is possible.