Brittle to ductile transition during compression of glassy nanoparticles studied in molecular dynamics simulations

Understanding how nanoparticles deform under compression not only is of scientific importance but also has practical significance in various applications such as tribology, nanoparticle-based probes, and the dry grinding of raw materials. In this study, we conducted compression tests on model brittle glassy nanoparticles using molecular dynamics simulations. We found that during the early stages of plastic deformation, shear bands formed in a similar pattern regardless of the nanoparticle size. However, as the deformation continued, dominant cracks emerged in large nanoparticles while being suppressed in smaller ones. This size-dependent brittle-to-ductile transition can be explained by a simple model based on Griffith's theory. We also investigated the effect of the surface stress state on fracture using thermally tempered nanoparticles. We observed that the presence of compressive surface stress strengthened the nanoparticle by suppressing crack formation, even when a pre-notch was present. On the other hand, tensile surface stress had the opposite effect. Interestingly, nanoparticles with both tensile and compressive surface stress promoted shear deformation, which could potentially compromise the mechanical performance of tempered glass despite delayed crack formation.

Automated summary

Understanding the deformation behavior of nanoparticles under compression is important for both scientific research and practical applications. Using molecular dynamics simulations, compression tests were conducted on brittle glassy nanoparticles. It was found that shear bands formed in a similar pattern during the early stages of plastic deformation, regardless of the nanoparticle size. However, as the deformation progressed, dominant cracks appeared in large nanoparticles while being suppressed in smaller ones, exhibiting a size-dependent brittle-to-ductile transition. The effect of surface stress on fracture was also investigated, revealing that compressive surface stress strengthened the nanoparticles by suppressing crack formation, while tensile surface stress had the opposite effect. Nanoparticles with both tensile and compressive surface stress promoted shear deformation, potentially compromising the mechanical performance of tempered glass.