The normal-auxeticity mechanical phase transition in graphene
BH Deng and J Hou and HX Zhu and S Liu and E Liu and YF Shi and Q Peng, 2D MATERIALS, 4, 021020 (2017).
When a solid object is stretched, in general, it shrinks transversely. However, the abnormal ones are auxetic, which exhibit lateral expansion, or negative Poisson ratio. While graphene is a paradigm 2D material, surprisingly, graphene converts from normal to auxetic at certain strains. Here, we show via molecular dynamics simulations that the normal-auxeticity mechanical phase transition only occurs in uniaxial tension along the armchair direction or the nearest neighbor direction. Such a characteristic persists at temperatures up to 2400 K. Besides monolayer, bilayer and multi-layer graphene also possess such a normal- auxeticity transition. This unique property could extend the applications of graphene to new horizons.
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