Nonadiabatic Study of Dynamic Electronic Effects during Brittle Fracture of Silicon

It has long been observed that brittle fracture of materials can lead to emission of high energy electrons and UV photons, but an atomistic description of the origin of such processes has lacked. We report here on simulations using a first-principles-based electron force field methodology with effective core potentials to describe the nonadiabatic quantum dynamics during brittle fracture in silicon crystal. Our simulations replicate the correct response of the crack tip velocity to the threshold critical energy release rate, a feat that is inaccessible to quantum mechanics methods or conventional force-field-based molecular dynamics. We also describe the crack induced voltages, current bursts, and charge carrier production observed experimentally during fracture but not previously captured in simulations. We find that strain-induced surface rearrangements and local heating cause ionization of electrons at the fracture surfaces.