New candidate to reach Shockley-Queisser limit: The DFT study of orthorhombic silicon allotrope Si(oP32)

In the present study, the unit cell parameters and atomic coordinates are predicted for the Pbcm orthorhombic structure of Si(oP32) modification. This new allotrope of silicon is mechanically stable and stable with respect to the phonon states. The electronic structure of Si(oP32) is calculated for LDA and HSE06 optimized structures. The band gap value E-g = 1.361 eV predicted for Si(oP32) is extremely close to the Shockley-Queisser limit and it indicates that the Si(oP32) modification is a promising material for efficient solar cells. The frequencies of Raman and Infrared active vibrations is calculated for allotrope Si(oP32).