Theoretical and molecular dynamics studies of critical resolved shear stress for rhombohedral twinning of sapphire

• Published in: Computational materials science 2024-09, Vol.244, p.113278, Article 113278
• Main Authors: Xi, Dalei, Du, Yiyang, Nagaraj, Aditya, Kwon, Suk Bum, Kim, Dae Nyoung, Min, Sangkee, Kim, Woo Kyun
• Format: Article
• Language: English
• Subjects: Critical resolved shear stress (CRSS); Molecular dynamics simulation; Rhombohedral twinning; Sapphire
• ISSN: 0927-0256
• DOI: 10.1016/j.commatsci.2024.113278

Single crystalline sapphire (α-Al2O3) 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. [Display omitted] •MD simulations of compression test on sapphire to study activation of rhombohedral twinning.•CRSS is calculated under various conditions (temperature, strain rate, model size).•A thermal activation-based model predicts CRSS for various conditions.•The model effectively captures the key trends in CRSS observed in MD simulations.