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Single crystalline sapphire (-) possesses superior mechanical, thermal, chemical, and optical properties over a wide range of temperatures and pressure conditions, allowing it for a broad spectrum of industrial applications. For the past few decades, research has aimed at comprehensive understanding of its plastic deformation mechanisms under mechanical loading. In this study, we have employed molecular dynamics (MD) simulations to study rhombohedral twinning of sapphire, which is of critical importance in understanding the plastic deformation of sapphire as one of most commonly observed deformation modes. Since the critical resolved shear stress (CRSS) plays a pivotal role in describing the activation of slip systems, it is adopted in this study as the key parameter for analysis. The CRSS is calculated during the uniaxial compression test of a cubic sapphire crystal, oriented to exclusively activate rhombohedral twinning deformation, under simulation conditions such as temperature, strain rate, and system size. Furthermore, a theoretical model of CRSS is constructed based on theories of thermal activation processes, then empirically fitted to CRSS data gathered from the MD simulations. This model accurately captures the relationships between CRSS and external parameters including temperature, strain rate, and system size and shows excellent agreements with the simulation results. 

Biological materials have consistently intrigued researchers due to their remarkable properties and intricate structure–property-function relationships. Deciphering the pathways through which nature has bestowed its exceptional properties represents a complex challenge. The hierarchical architectures of biomaterials are recognized as the basis for mechanical robustness. Moreover, it is well-established that the intriguing properties of biomaterials arise primarily from the architecture at the nanoscale, particularly the abundant carefully designed interfaces. Driven by the diverse functionality and the increasing comprehension of the underlying design mechanisms in biomaterials, substantial endeavors have been directed toward emulating the architectures and interactions in synthetic materials. By reviewing atomistic modeling of nacre, wood, and coconut endocarp, in this work, we aim at highlighting the significant role of atomistic modeling in revealing nanoscale strengthening and toughening mechanisms of biomaterials, subsequently advancing the development of bioinspired material.