Pressure-Induced Insulator-Metal Phase Transition in Si₂Te₃ from First-Principles Calculations

Silicon telluride (Si₂Te₃) is a layered two-dimensional p-type semiconductor with unique structural variability arising from the presence of silicon dimers filling two-third of the allowed sites with different orientations. A recent experiment reported that the material undergoes an insulator-metal phase transition under hydrostatic pressure at 9.5 GPa. Using the evolutionary algorithm combined with the first-principles density functional theory calculations, we identify two metallic phases of Si₂Te₃ to account for the observation. The calculated insulator-metal transition pressures agree very well with the experimental results. Furthermore, we find that the external hydrostatic pressure causes the semiconducting phase to undergo an indirect-direct-indirect band gap transition. Such pressure-induced gap transitions could be beneficial for potential applications of the material.