Determining the Complete Stability of Calcite Kink Sites: Real vs Ideal

Kink sites play a pivotal role inthe growth and dissolution ofmaterials at the solid-liquid interface. Despite this, littleis known about the thermodynamic stability of such sites. Calciumcarbonate, in the form of calcite, is one of the most abundant biomineralsand a natural means of carbon sequestration in the environment. Here,we present a complete determination of the standard free energiesfor all 16 individual kink sites for the significant case of the calcite(101 4)-water interface using both alchemical- and pathway-basedsimulation techniques. The results reveal the importance of distinguishingbetween real and ideal ion-binding free energies at surfaces, especiallyfor calcite-water, where the interfacial potential can altervalues by more than 100 kJ/mol per site. Individual kink site stabilitiesare found to show variations in excess of 60 kJ/mol, which can helpexplain the observed differences in growth rates between the two distinctsteps of calcite.