Strain-induced formation of surface defects in amorphous silica: a theoretical prediction.

We present a prediction for the formation of surface defects in a thin amorphous silica layer during relaxation of externally imposed stresses and strains, based on extensive ab initio molecular dynamics calculations. Our calculations show that the application of a biaxial compressive stress leads to the creation of edge-sharing tetrahedron and/or silanone defects at the silica surface, which turns out to facilitate strain relief with irreversible structural changes in the silica layer. We also discuss a possible correlation between the predicted formation of surface defects and the observed enhanced surface reactivity of amorphous silica under compressive strain conditions.