Tetra-SiC - New allotrope of 2D silicon carbide

VV Hoang and NH Giang and TQ Dong and TTT Hanh, COMPUTATIONAL MATERIALS SCIENCE, 162, 236-244 (2019).

DOI: 10.1016/j.commatsci.2019.02.037

Formation and atomic structure of two-dimensional (2D) tetra-SiC (containing entirely tetragons) are studied by molecular dynamics (MD) simulations. Models contain 6400 atoms (3200 Si atoms and 3200 C ones) interacted via so-called Vashishta's interatomic potentials. We compress initially perfect planar SiC with honeycomb structure (hexa-SiC) at three different temperatures (below and above melting point) step by step and we find hexa-tetra 2D SiC phase transition. Tetra-SiC sample obtained at temperature significantly below melting point exhibits the best quality which contains the lowest concentration of defects (non- tetragons). This tetra-SiC is stable over a wide range of density and temperature. On the other hand, we cool the obtained tetra-SiC to room temperature and it is also stable at room temperature. Evolution of various structural and thermodynamic quantities upon compression is studied and we find that it exhibits a first-order-like phase transition behavior. Detailed analysis of structure of the obtained tetra-SiC is shown via coordination number and bond-angle distributions, ring statistics, 2D visualization of atomic configurations etc. Moreover, important quantities of mechanical behaviors such as Young modulus and Poisson's ratio of the sample are found and discussed. DFT calculations show that flat tetra-SiC is stable with a band gap of around 0.97 eV. Our prediction of the existence of this new allotrope of 2D SiC can serve as a guide for further investigation in this direction including fabrication of material in practice.

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