Anisotropic mechanical response, high negative thermal expansion, and outstanding dynamical stability of biphenylene monolayer revealed by machine-learning interatomic potentials

Abstract

Recently, the two-dimensional (2D) biphenylene network with a specific arrangement of four-, six-, and eight-membered carbon rings has been fabricated over the gold surface via a two-step polymerization technique (Science 372(2021), 852). Inspired by the aforementioned experimental advance and exciting physics of full-carbon 2D lattices, for the first time, we herein employ machine-learning interatomic potentials (MLIPs) to explore the mechanical properties, failure behavior, dynamical stability, and thermal expansion of the biphenylene monolayer. The remarkable accuracy of the developed MLIP-based models is concluded by comparing the predicted direction-dependent uniaxial stress-strain relations and failure mechanism of the biphenylene monolayer with those obtained by density functional theory simulations. Analysis of phonon dispersion relations reveals an outstanding dynamical stability of the biphenylene monolayer. Similarly to graphene, the biphenylene network also exhibits a negative thermal expansion, but with around twice the value of graphene at room temperature. We also studied the temperature effect on the tensile strength and failure strain of the biphenylene monolayer. The presented results provide a useful vision concerning the thermo-mechanical properties of the 2D biphenylene network.