New Trends in Chemistry at Steps Due to Mechanical Stress and Relevance to Corrosion

Theoretical investigation of surface chemistry has had many successes including but not limited to surface structure, phase stability, chemical kinetics, electrochemical modeling, and solution phase chemistry.  Yet developed is a method for the investigation of the influence of an arbitrarily applied stress to an arbitrary surface structure.  In this work the linear elastic theory of mechanics is applied to the surface structure to investigate precisely this.  Chemisorption over a wide variety of late transition metals is studied and it is shown that the change in chemisorption energy due to an applied stress is non-uniform.  For example, when stress is applied parallel to or orthogonal to the line of a step the chemical response is not necessarily the same.  Furthermore, the chemical response at defects is inconsistent between materials.  These phenomena are demonstrated, analyzed in terms of known theory such as d-band theory. It is shown that at steps a departure from d-band theory occurs due to mechanical contributions to the binding energy of species under stress. This mechanical contribution to chemistry provides a new framework to consider when thinking of surface chemistry under stress and is discussed in terms of crack tip chemistry.