Hexa ⇆ tetra silicene crystal-crystal phase transition

Formation of confined crystalline tetra-silicene (t-silicene) from crystalline hexa-silicene (h-silicene) via compression, and the reverse transition from the obtained t-silicene to h-silicene via heating, are studied by molecular dynamics (MD) simulations. Models contain 6400 Si atoms interacted via the new version of the Stillinger-Weber potential. While t-silicene can be obtained via compression of the crystalline h-silicene at various temperatures, we find that the best quality samples (with the highest fraction of tetragons) are obtained at high temperatures but still well below the melting point. Such t-silicene is stable over a wide range of pressure and temperature. Evolution of the structural characteristics of samples and various thermodynamic quantities upon compression is studied. Detailed analysis of the structure of t-silicene at 300 K is presented via radial distribution function, coordination number and bond-angle distributions, ring statistics and interatomic distance distribution, as well as 2D visualisation of the atomic configurations. Various types of structural defects of t-silicene are found and discussed. In addition, heating of the obtained t-silicene is shown to lead first to the reverse tetra-to-hexa silicene phase transition, and then to the melting of h-silicene. Evolution of the structural characteristics of the samples and of the thermodynamic quantities upon heating are considered. Atomic mechanism underlaying the tetrahexa phase transitions is discussed.