Anisotropic mechanical response of a 2D covalently bound fullerene lattice

Contrary to the monotype intercell connection in a hexagonal structure material, newly synthesized stable monolayer C₆₀ fullerene (mC₆₀) lattice possesses two kinds of intercell connection, and anisotropic properties are thus expected. Herein, we have investigated the anisotropy mechanical properties of the mC₆₀ using first-principles calculations within the framework of density functional theory (DFT) and theoretical analysis. Uniaxial tensile properties of mC₆₀ are orientation-dependent, and the ultimate tensile strength and the work-to-fracture of mC₆₀ reach their maxima at 15° and minima at 75°, respectively. A theoretical expression, based on strain-governed bond failure criterion, has been developed for the strength-loading direction relationship of mC₆₀. The theory captures well with the orientation-dependent strength from DFT calculations. We further illustrate that mC₆₀'s band gap may be largely tuned through strain engineering. Our atomistic insights and the theoretical on the structure – mechanical property relationship might be helpful in the exploring of the functioning and application of mC₆₀, which may be further generalized to the mechanical analysis of other monolayer lattices.