Fig. 7: Optical properties of the predicted Si2He and Si allotropes.

Imaginary part of the dielectric functions of oP36-Si2He, mC12-Si2He, and the three silicon alltropes (oC24-Si, tP6-Si, and mC8-Si) calculated with the HSE06 functional, as well as the reference air mass 1.5 (AM1.5) solar spectral irradiance62 and CD-Si.