silicon properties

Fracture stress depends on surface roughness. Hence, it varies.

Michael Dahms

The fracture strength of SiO2... Silica , not silicon (or silicone) will range from nearly the same high to the same low.

For brittle crack-surface-crack sensitive materials like glass, silica and silicon, it is perfectly meaningless to imagine a definitive value of fracture stress.

It is sort of meaningful to imagine a value of fracture stress for a highly specific way of making and handling of such materials.

Brittle fracture is not well covered by looking for numbers with no physical understanding of the process and the intrinsic statistical nature of brittle fracture as well.

If this is important to you, it is time to dig into brittle fracture with some of the many articles and books on the subject.

Jim

I would hazard a guess that the critical resolved shear stress to fracture would be a better classifier parameter for brittle materials. The original poster mentioned silicon 111 crystal. Si is diamond cubic and the [111] planes would be the preferred slip planes.