Amorphous and 'crystalline' penta-silicene

Atomic structure, thermodynamic and mechanical behaviours of the penta-silicene (p-silicene) obtained by cooling from the melt are studied by the molecular dynamics (MD) simulations. We find thatp-silicene can 'naturally' form from the liquid state using the appropriate interatomic potential, density and buckling. The charge-optimised many body (COMB) potential is employed. Depending on the cooling rate used in simulations, 'crystalline' or amorphousp-silicene can be obtained. 'Crystallisation' and glass transition temperatures (TX=1620KandTg=1230K, respectively) have reasonable values compared to those of the hexa-silicene (h-silicene). We find that the Poisson's ratio of the obtained 'crystalline'p-silicene is positive unlike the negative one found for thep-graphene. The reasons for the formation ofp-silicene instead of tetra-silicene (t-silicene) are analysed and discussed, i.e. 2D liquid silicene with COMB potential has a significant fraction of pentagons which grow with decreasing temperature, unlike 2D liquid silicene with the Stillinger-Weber potential.