Finally, the major role in the recovery of rs-ZnO plays the underlying nucleation mechanism of the reverse transition, which implies non-uniform tensile strength along some crystallographic directions, in good agreement with ab initio predictions. Once the oversaturation becomes important (in the terms of pressure, p tr -p eq ~ -4 GPa for the reverse transition), the rs-ZnO  w-ZnO transition becomes possible and is often observed (at least partially).