The mechanical properties of the scratched surface for silica glass by molecular dynamics simulation

• The model of silica glass is established by the approach of melting–quenching.
• We studied the mechanical properties of the scratched surface.
• The hardness of the silica glass increased 18% after once scratching.
• The scratched surface can help the plastic deformation.
• These changes are ascribed to the formation of fivefold defect.

In order to study the mechanical properties of the processed surface for silica glass, a nanoscratch of the silica glass is built based on molecular dynamics method and a nanoindentation is performed on the scratched surface subsequently. The model of silica glass is established by using the approach of melting–quenching and the forming mechanism of the microscopic voids in the process of preparation is analyzed. During nanoindentation, the mechanical properties of the machined surface and the original surface are compared. The results show that the microscopic cavity in the silica glass will form in the cooling process due to the accumulation of large rings generating by the restructuring of the Si–O bonds. The hardness and plastic of the scratched surface will improve after the abrasive sweeps away. The deformation mechanism of the model during nanoscratch is densification rather than plastic flow, which is the reason of the increasing of the surface hardness. According to the further analysis of the atomic concentration areas in the scratched surface, it is found that the fivefold defect is responsible for the change of the plastic behavior.