Observation of calcite (101̄4) surface by AFM in air and surface structure analysis

Abstract

Natural calcite single crystal from Chihuahua Mexico was treated at 873 K for 1.5 h in a furnace_and cooled in air. Thirty minutes later it began to cleave spontaneously by residual thermal stress along (101̄4) plane in a desiccator. An atomic force microscope (AFM) was used to observe the cleaved (101̄4) surface structure in air. Atomic scale AFM images were obtained for the first time in air, which show the periodicity of regular atomic arrangement of (101̄4) surface. The lateral linear dimensions of surface parameters from AFM images show a general agreement with those obtained from X-ray diffraction measurement for bulk material. It was found that there was 0.06 nm difference in height of alternating oxygen atom rows in the AFM images. The difference was considered due to reconstruction of calcite surface structure under the balance of atomic interaction on the surface in which half of [CO3]2- rotated by 35.4 ± 5.2° around the C-O bond axis lying in the (101̄4) surface to reach a small slope with respect to the (101̄4) surface.