Ripplocation Boundaries and Kink Boundaries in Layered Solids

Ripplocations - best defined as an atomic scale ripple and characterized by oppositely signed ripplocation boundaries (RBs) – have recently been shown to be the underlying mechanism responsible for buckling in layered crystalline solids (LCS) such as graphite, mica, and the MAX phases. The malefactor for the deformation of LCS for more than half a century has been basal dislocations (BDs) which manifest themselves into kink boundaries (KBs) at high stresses. Since the inception of ripplocations, much work has gone into deciphering the fundamental deformation mechanism of LCS, and other layered systems such as steel sheets and playing cards. To develop a thorough understanding of the phenomena, we collected data via retrospective analysis of the literature on RBs and KBs that was carried out to date. Furthermore, to support this study we also provide new molecular dynamics (MD) data to analyze the deformation behavior in graphite through bending tests to substantiate our hypothesis. Based on this work, it is evident that KBs and RBs are distinctive in many ways; i) RBs are reversible in nature in that the system can return to its original state after deformation while KB formation only occurs when the material has been plastically deformed, ii) Atomical observations show that RBs have rounded edges as opposed to the sharp, pointy edges seen in KBs, iii) RBs are associated with high stresses at their surface which is absent in the case of KBs, and lastly iv) At extreme strains, RBs transform into KBs. By employing several - mostly past – and present investigations we intend to fundamentally unravel the differences between these atomic boundaries occurring in layered systems. The consequences of this study will help elucidate the deformation mechanics of layered systems in tens of orders of magnitudes, from the nanoscale to the geological scale.