Electronic, optical, and mechanical properties of a novel high-symmetry silicon carbide predicted using...

To explore more silicon carbide structures with superior properties, a novel silicon carbide with a highly symmetric truncated octahedral structure, named Pm3n-SiC, was investigated using first-principles methods based on density functional theory (DFT). This silicon carbide structure belongs to the cubic crystal system and $\text{PM}\overline{3}N$ symmetry group. The results show that Pm3n-SiC has a formation enthalpy of - 0.321 eV. Its phonon dispersion spectrum exhibits no imaginary frequencies, and its independent elastic constants satisfy the mechanical stability criteria. This finding indicates that Pm3n-SiC is readily synthesizable and exhibits both dynamic and mechanical stability. According to Chen's model, the Vickers hardness is estimated to be approximately 16.3 GPa, and the universal elastic anisotropy index $A^U$  = 0.57, which is a medium-hardness anisotropic material. Band structure and optical property analysis revealed that Pm3n-SiC is an indirect bandgap semiconductor with a bandgap of 2.732 eV. It exhibits strong transmittance in both the infrared and visible light regions, indicating its potential for optoelectronic applications.

The calculations were performed using Density Functional Theory (DFT) as implemented in the Cambridge Sequential Total Energy Package (CASTEP). In this study, the material properties were analyzed using the GGA-PBE method. Since the PBE functional is generally known to underestimate bandgap values, the bandgap was also calculated using the HSE06 functional. Additionally, the elastic modulus was estimated using the Voigt-Reuss-Hill (VRH) approximation, and the Vickers hardness was evaluated based on Chen's model.