CI24‐Si: a Semiconducting Silicon Phase with an All‐sp3 Bonding Network

Abstract

AbstractA silicon allotrope which consists of 24 atoms in a body centered cubic cell and displays an symmetry (termed as cI24‐Si) with a mass density of 2.38 g/cm3, is theoretically investigated. This silicon phase has an all‐sp3 network with hexagons. Phonon dispersion confirms its dynamical stability and elastic constant implies it is mechanically stable. The analysis of electronic band structure performing by HSE06 functional shows that cI24‐Si is an indirect semiconductor with a small band gap of 0.83 eV. Additionally, its direct band gap is only 0.02 eV larger than the indirect band gap, indicating that cI24‐Si possesses a quasi‐direct band gap. The calculations of imaginary part of dielectric function and optical absorption for cI24‐Si show that it has better optical properties than diamond‐like Si−I phase as it can capture more sunlight from visible to ultraviolet range. To provide more characterizations for future experimental observations, X‐ray diffraction patterns and Raman spectra are also theoretically simulated. Due to its small band gap, cI24‐Si may possess potential electronic, optical and photovoltaic applications.