Force-penetration curves for nano-indented barite (001) surfaces were recorded, and the microstructures were imaged using atomic force microscopy. Pop-ins in the penetration curves were correlated with the appearance of permanent concave traces in the surface and with the emission of specific dislocations; some of which could cross-slip and result in terraces which wound around the nano-indentation contact point. The dislocations identified here could be related to special deformation mechanisms which had previously been reported for metals. The effective shear stress, which resulted in permanent traces associated with plasticity, as obtained from the atomic force microscopy data, was compared with theoretical estimates for a perfect crystal.

Dislocation Generation and Motion at the Incipient Stages of Surface Plasticity in Barite. A.Asenjo, J.M.Rojo: Philosophical Magazine, 2007, 87[26], 3959-66