Atomistic deformation mechanism of silicon under laser-driven shock compression

Silicon (Si) is one of the most abundant elements on Earth, and it is the most widely used semiconductor. Despite extensive study, some properties of Si, such as its behaviour under dynamic compression, remain elusive. A detailed understanding of Si deformation is crucial for various fields, ranging from planetary science to materials design. Simulations suggest that in Si the shear stress generated during shock compression is released via a high-pressure phase transition, challenging the classical picture of relaxation via defect-mediated plasticity. However, direct evidence supporting either deformation mechanism remains elusive. Here, we use sub-picosecond, highly-monochromatic x-ray diffraction to study (100)-oriented single-crystal Si under laser-driven shock compression. We provide the first unambiguous, time-resolved picture of Si deformation at ultra-high strain rates, demonstrating the predicted shear release via phase transition. Our results resolve the longstanding controversy on silicon deformation and provide direct proof of strain rate-dependent deformation mechanisms in a non-metallic system

Atomistic deformation mechanism of silicon under laser-driven shock compression

Silicon (Si) is one of the most abundant elements on Earth, and it is the most important and widely used semiconductor, constituting the basis of modern electronic devices. Despite extensive study, some properties of Si remain elusive. For example, the behaviour of Si under high pressure, in particular at the ultra-high strain rates characteristic of dynamic compression, has been a matter of debate for decades. A detailed understanding of how Si deforms is crucial for a variety of fields, ranging from planetary science to materials design. Simulations suggest that in Si the shear stress generated during shock compression is released inelastically, i.e., via a high-pressure phase transition, challenging the classical picture of relaxation via defect-mediated plasticity. However, experiments at the short timescales characteristic of shock compression are challenging, and direct evidence supporting either deformation mechanism remain elusive. Here, we use sub-picosecond, highly-monochromatic x-ray diffraction to study (100)-oriented single-crystal Si under laser-driven shock compression. We provide the first unambiguous, time-resolved picture of Si deformation at ultra-high strain rates, demonstrating the predicted inelastic shear release. Our results resolve the longstanding controversy on silicon deformation under dynamic compression, and provide direct proof of strain rate-dependent deformation mechanisms in a non-metallic system, which is key for the study of planetary-relevant materials

Praxial music education: A critical analysis of critical commentaries

Since its publication in 1995, a significant literature has developed around David J. Elliott’s praxial philosophy of music education, as explained in Music Matters: A New Philosophy of Music Education. This literature includes a range of commentaries in journals, books, edited books, and dissertations. Although Elliott has replied to some positive and negative commentaries since 1995, he has not addressed several adverse discussions by leading music education philosophers. Accordingly, we posit that there is an important gap in music education’s philosophical discourse that may cause some music education students and researchers to accept or reject important criticisms of Elliott’s praxialism without sufficient information or reflection. In this article we analyze several critiques of Elliott’s praxialism. Our discussion divides into three sections related to major topics presented in the praxial philosophy particularly and music education generally: music making, music listening and musical works, and musical values. Each section presents (a) critics’ evaluations of Elliott’s position on a given topic, and (b) Elliott’s stated position on that topic, as explained in Music Matters. Where pertinent, we consult the views of other scholars on specific topics. We end each section with brief reflections on critics’ claims, reserving our final evaluations for the concluding section