Phase transition in twinned nanolayered silicon structures under uniaxial compression: Molecular dynamics simulations and first-principles total-energy calculations

Molecular dynamics simulations and first-principles total-energy calculations were carried out to investigate the behavior of nanolayered (111) twinned silicon structures under uniaxial compression. The diamondlike silicon structure inside the thin (<3 nm) twin layers was found to transform to the orthorhombic structure (space group Fmmm) at similar to 25 GPa under uniaxial compression and to the tetragonal structure (space group I4/mmm) upon decompression. The first structural transformation is a first-order phase transition and the new structure is characterized by an increased failure stress above 37 GPa. First-principles pseudopotential calculations confirmed the formation of the tetragonal phase and showed that both the orthorhombic and tetragonal phases would possess metal properties.