First principles investigation of the structural, electronic, and optical properties of new c-Si12 silicon allotrope with a cubic structure

Abstract

In this paper, some structural, electronic, and optical properties of c-Si12 silicon allotrope was investigated based on the density functional theory approach. The results were compared to some of silicon allotropes. The structural results show that both the optimal cubic lattice constant and Si–Si bond length in the c-Si12 structure are larger than the diamond-Si one, although the bulk modulus for the c-Si12 structure is smaller than the diamond-Si and other Si allotrope structures. The electronic results indicate that c-Si12 structure is a semiconductor with an indirect band gap having an energy distance about 0.187 eV between its indirect and direct band gaps. In the optical properties section, the dielectric function, energy loss function, refractive index, and reflectivity of the c-Si12 structure were investigated and compared to the experimental data for the diamond silicon allotrope. Our results indicate that in the visible range, the optical absorption of the c-Si12 structure is larger than the diamond-Si which implies the promising optical properties of the c-Si12 structure and its advantage with respect to the diamond-Si one.