Abstract
Plastically anisotropic/layered solids are ubiquitous in nature and understanding how they deform is crucial in geology, nuclear engineering, microelectronics, among other fields. Recently, a new defect termed a ripplocation–best described as an atomic scale ripple–was proposed to explain deformation in two-dimensional solids. Herein, we leverage atomistic simulations of graphite to extend the ripplocation idea to bulk layered solids, and confirm that it is essentially a buckling phenomenon. In contrast to dislocations, bulk ripplocations have no Burgers vector and no polarity. In graphite, ripplocations are attracted to other ripplocations, both within the same, and on adjacent layers, the latter resulting in kink boundaries. Furthermore, we present transmission electron microscopy evidence consistent with the existence of bulk ripplocations in Ti3SiC2. Ripplocations are a topological imperative, as they allow atomic layers to glide relative to each other without breaking the in-plane bonds. A more complete understanding of their mechanics and behavior is critically important, and could profoundly influence our current understanding of how graphite, layered silicates, the MAX phases, and many other plastically anisotropic/layered solids, deform and accommodate strain.
Highlights
Anisotropic/layered solids are ubiquitous in nature and understanding how they deform is crucial in geology, nuclear engineering, microelectronics, among other fields
It has long been assumed that layered silicates, ice, the MAX phases, and graphite, etc. deform predominantly by the nucleation and slip of basal dislocations (BDs)[1,2,3,7,8,9]
Many layered solids have been classified as kinking nonlinear elastic (KNE), including the MAX phases[4], mica[10], graphite[11] and many ionic ceramics[12,13]
Summary
A group of four graphite unit cells at either end was fixed rigid, and one of the ends was displaced inwards by 2% of the x-axis translation vector every step, followed by conjugate gradient minimization. This process was performed until the total displacement was equal to 4 times the translation vector. (iii) Bulk ripplocations (BRs) nucleated by straining an arbitrary layer within a system of 60 layers periodic in the z-axis (Fig. 1e–h). In this figure only 5 layers of the 60 are shown, and, (iv) BRs nucleated by straining the middle layer in a tri-layer configuration (Fig. 1i–k). The GPA analysis was performed using g =(0001) and (1120)
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