Mechanical and electronic properties of a novel cubic silicon allotrope with direct band gap: First-principles calculation

In the present manuscript, a cubic cage-like silicon allotrope, designated as Si₉₆I and belonging to the Fd-3 m space group, is put forward. Employing first-principles calculations, a detailed exploration and analysis of its structural, mechanical, and electronic characteristics were carried out. Under normal ambient pressure conditions, Si₉₆I demonstrates remarkable mechanical, kinetic, and thermal stabilities. Distinguishing itself from diamond-Si, Si₉₆I exhibits ductility and possesses a notably low density of 1.409 g/cm³, which can be attributed to its relatively large pore structure. Furthermore, in terms of elastic mechanics, the anisotropy of this novel silicon material is found to be less significant than that of diamond silicon. This implies that the direction has a lesser impact on its elastic modulus. Most importantly, Si₉₆I is identified as a semiconductor with a direct and narrow band gap of 0.73 eV, endowing it with great potential to fuel future advancements in the optoelectronic industry as well as in the realm of new energy materials. The superior visible light absorption characteristics also make it a highly promising candidate material for next-generation solar cells.