LAUSR

By employing an ab initio evolutionary algorithm, we predict two novel metastable structures whose energies are just higher than g-SiC but lower than other two-dimensional (2D) SiC siligraphenes reported so far. One is composed of 4-6-8 C–Si rings named tho-SiC siligraphene and the other one is composed of 5-6-8 rings named pho-SiC siligraphene. They are almost equal in energy, but interestingly, our calculations demonstrate that tho-SiC siligraphene is a semiconductor like g-SiC, while pho-SiC siligraphene is a 2D metal. Additionally, unlike g-SiC which is very easy to switch from a direct band gap to indirect band gap semiconductor and exhibits homogenous isotropy characteristic under biaxial strains, tho-SiC siligraphene keeps a consistently direct band gap from 1.02 eV to 1.98 eV as the uniaxial strain increases from −9% to 9% and it shows strong anisotropic electronic structures. The obtained calculation results indicate that tho-SiC siligraphene may be a better candidate than g-SiC in the application of light-emitting devices in the future.