Phase transformations of mono-crystal silicon induced by two-body and three-body abrasion in nanoscale

This article is focused on understanding the structural phase transformations of mono-crystalline silicon induced by nanoindentation, two-body and three-body abrasion at the nanoscale using the large-scale molecular dynamics simulation. The evolution and distribution of the possible phases are discussed in terms of coordination number (CN), radial distribution function (RDF), bond angle distribution function (ADF) and atom type tracking. The results show a new phase transformation route that is an initial diamond cubic silicon turns into high density amorphous (HDA) beneath the moving particle and then transforms into low density metastable amorphous (LDMA) behind the particle in both two-body and three-body abrasion. Considering the different phase transformation between nanoindentation and two/three-body abrasion, a stress criterion is proposed to predict the phase transformation, which can be generally applied to hydrostatic pressure experiment, nanoscale uniaxial compression and nanoindentation. For nanoindentation, a common misunderstanding of a metastable phase is clarified, which is also observed in front of the moving particle in two/three-body abrasive.