POISONING OF CALCITE GROWTH VIEWED IN THE ATOMIC FORCE MICROSCOPE (AFM)

We Present real-time, in situ atomic force microscope (AFM) observatio ns of poisoning of calcite. This technique allows direct observation o f chemically induced changes in the velocity and morphology of monomol ecular steps less than 1 nm high, and direct imaging of adsorbates. Ph osphonates and phosphates attach directly but reversibly onto growth s teps above a threshold concentration, and further growth is inhibited until the poison is removed. In contrast, magnesium ions and NaCl have much weaker effects on growth. All additives studied changed step sha pes, and HEDP and SHMP modify re-growth morphology, leading to spicula r growth on rhomb faces.