A study on phase transformation of monocrystalline silicon due to ultra-precision polishing by molecular dynamics simulation

A three-dimensional molecular dynamics (MD) simulation is conducted to investigate the material removal mechanism of monocrystalline silicon by mechanical polishing at atomistic scale with diamond abrasives. By monitoring relative positions of atoms in the monocrystalline silicon specimen, the microstructure transformation of monocrystalline silicon is clearly identified and analyzed. The phase transformation is accomplished under extreme conditions with high temperature and huge hydrostatic pressure, and as a result the silicon microstructure transforms from the four-coordinated diamond cubic structure (Si-I) to the six-coordinated body-centered tetragonal structure (β-silicon). The values of local pressure and temperature are consistent with previous experimental results. In addition, the force between the diamond abrasive and specimen indicates the occurrence of phase transformation in the specimen. The potential energy of each atom is also calculated, which provides us an effective approach to analyze the energy variation of atoms in the mechanism of material deformation and the formation of machined surface after ultra-precision polishing