2015/08/31 by Shiva Rudraraju, Anton Van der Ven, Krishna Garikipati · 64 citations
Materials Science · Physics and Astronomy · #Boron and Carbon Nanomaterials Research #Context (archaeology) #Density functional theory #Elasticity (physics) #Microstructure #Microstructure and mechanical properties #Phase (matter) #Phenomenological model #Shape Memory Alloy Transformations #Spinodal #Spinodal decomposition #Strain energy #cond-mat.mtrl-sci #physics.chem-ph
paper · pdf · doi:10.1038/npjcompumats.2016.12
published in npj Computational Materials 2(1) (Nature Portfolio) · Published in Nature npj Computational Materials. Movies listed in the supplementary information available in the "Supplementary Information" section under: http://www.nature.com/articles/npjcompumats201612
openalex publication_date 2016/06/10 · openalex created_date 2016/06/24 · arxiv created 2016/09/28 · arxiv updated 2016/09/29 · openalex updated_date 2026/08/06
Abstract We present a phenomenological treatment of diffusion-driven martensitic phase transformations in multi-component crystalline solids that arise from non-convex free energies in mechanical and chemical variables. The treatment describes diffusional phase transformations that are accompanied by symmetry-breaking structural changes of the crystal unit cell and reveals the importance of a mechanochemical spinodal, defined as the region in strain–composition space, where the free-energy density function is non-convex. The approach is relevant to phase transformations wherein the structural order parameters can be expressed as linear combinations of strains relative to a high-symmetry reference crystal. The governing equations describing mechanochemical spinodal decomposition are variationally derived from a free-energy density function that accounts for interfacial energy via gradients of the rapidly varying strain and composition fields. A robust computational framework for treating the coupled, higher-order diffusion and nonlinear strain gradient elasticity problems is presented. Because the local strains in an inhomogeneous, transforming microstructure can be finite, the elasticity problem must account for geometric nonlinearity. An evaluation of available experimental phase diagrams and first-principles free energies suggests that mechanochemical spinodal decomposition should occur in metal hydrides such as ZrH 2−2 c . The rich physics that ensues is explored in several numerical examples in two and three dimensions, and the relevance of the mechanism is discussed in the context of important electrode materials for Li-ion batteries and high-temperature ceramics.