0000000000083988
AUTHOR
Andrew L. Rohl
Resolving Point Defects in the Hydration Structure of Calcite (10.4) with Three-Dimensional Atomic Force Microscopy
It seems natural to assume that defects at mineral surfaces critically influence interfacial processes such as the dissolution and growth of minerals in water. The experimental verification of this claim, however, is challenging and requires real-space methods with utmost spatial resolution, such as atomic force microscopy (AFM). While defects at mineral-water interfaces have been resolved in 2D AFM images before, the perturbation of the surrounding hydration structure has not yet been analyzed experimentally. In this Letter, we demonstrate that point defects on the most stable and naturally abundant calcite (10.4) surface can be resolved using high-resolution 3D AFM-even within the fifth h…
Model of scanning force microscopy on ionic surfaces.
We present a theoretical model of the scanning force microscope using an atomistic simulation technique for the interaction between a crystalline sample and a tip nanoasperity combined with a semi- empirical treatment of the mesoscopic van der Waals attraction between tip and surface, and the macroscopic parameter of cantilever deflection. For the nanoasperity at the end of the tip, we used a neutral and a protonated (MgO${)}_{32}$ cube, which model a hard tip made of oxide material. Static calculations based on total-energy minimization were used to determine the surface and tip geometries and total energy as a function of tip position. Scan lines of the perfect (001) surfaces of NaCl and …
Properties of small clusters at ionic surfaces: (NaCl)nclusters (n=1–48) at the (100) MgO surface
We have studied the geometry, binding energy, interaction with the surface, barriers for diffusion, optical absorption, and the possibility for their observation using atomic force microscopy of (NaCl${)}_{\mathit{n}}$ clusters (n=1--48) on the (100) MgO surface. We address the questions at which cluster size do the adsorbed molecules lose their identity and how do strained clusters accommodate the strain. The relation between the structure of initial molecular fragments adsorbed at the surface and the structure of the corresponding thick film is discussed. The results are compared with the calculated structures of the free clusters and the experimental data on the molecular-beam epitaxy of…