Confined tetra-silicene obtained by cooling from the melt

Abstract

Formation of confined tetra-silicene (t-silicene) from the melt is studied by molecular dynamics (MD) simulation. Models containing 6066 atoms interacted via Stillinger-Weber potential are obtained by cooling from 5000 K to 300 K. We find that t-silicene is formed with the broad buckling distribution ranged from 0.60 Å to 1.49 Å differed from unique buckling of 1.49 Å predicted by DFT calculations. Depending on the cooling rate used in simulations one can obtain crystalline or amorphous samples. Crystallization and glass transition temperatures are defined, namely, TX≈1950 K and Tg≈1350 K. These temperatures are higher than those found for hexa-silicene. Structural characteristics of models are studied in details via radial distribution functions (RDFs), coordination number, bond-angle, interatomic distance and buckling distributions plus ring statistics. In addition, 2D visualization of atomic configurations plus diffraction pattern of the models at 300 K is done in order to see in more details structure of the models. Main types of structural defects are defined and their role in chemico-physical performance of t-silicene is discussed. Although main structural units are tetragons, both amorphous and crystalline t-silicenes contain many rings differed from tetragons. According to our calculations, the Poisson ratio for the obtained t-silicene is positive. In order to clarify interatomic potential effects on the formation of t-silicene, the same simulation procedure is done with the reactive force field and intensive comparison is given.