Jin-Wu Jiang

Negative poisson’s ratio in single-layer black phosphorus

The Poissons ratio is a fundamental mechanical property that relates the resulting lateral strain to applied axial strain. Although this value can theoretically be negative, it is positive for nearly all materials, though negative values have been observed in so-called auxetic structures. However, nearly all auxetic materials are bulk materials whose microstructure has been specifically engineered to generate a negative Poissons ratio. Here we report using first-principles calculations the existence of a negative Poissons ratio in a single-layer, two-dimensional material, black phosphorus. In contrast to engineered bulk auxetics, this behaviour is intrinsic for single-layer black phosphorus, and originates from its puckered structure, where the pucker can be regarded as a re-entrant structure that is comprised of two coupled orthogonal hinges. As a result of this atomic structure, a negative Poissons ratio is observed in the out-of-plane direction under uniaxial deformation in the direction parallel to the pucker.

Mechanical properties of single-layer black phosphorus

The mechanical properties of single-layer black phosphrous under uniaxial deformation are investigated using first-principles calculations. Both Youngs modulus and the ultimate strain are found to be highly anisotropic and nonlinear as a result of its quasi-two-dimensional puckered structure. Specifically, the in-plane Youngs modulus is 44.0 GPa in the direction perpendicular to the pucker, and 92.7 GPa in the parallel direction. The ultimate strain is 0.48 and 0.20 in the perpendicular and parallel directions, respectively.

Thermal expansion in single-walled carbon nanotubes and graphene: Nonequilibrium Green’s function approach

The nonequilibrium Greens function method is applied to investigate the coefficient of thermal expansion (CTE) in single-walled carbon nanotubes (SWCNT) and graphene. It is found that atoms deviate about 1% from equilibrium positions at T=0 K, resulting from the interplay between quantum zero-point motion and nonlinear interaction. The CTE in SWCNT of different sizes is studied and analyzed in terms of the competition between various vibration modes. As a result of this competition, the axial CTE is positive in the whole temperature range, while the radial CTE is negative at low temperatures. In graphene, the CTE is very sensitive to the substrate. Without substrate, CTE has large negative region at low temperature and very small value at high temperature limit, and the value of CTE at T=300 K is

Isotopic effects on the thermal conductivity of graphene nanoribbons: Localization mechanism

-6\times 10^{-6}

Thermal conductance of graphene and dimerite

K

A nonequilibrium Green’s function study of thermoelectric properties in single-walled carbon nanotubes

^{-1}

Mechanical properties and fracture behavior of single-layer phosphorene at finite temperatures

which is very close to recent experimental result,

Minimum thermal conductance in graphene and boron nitride superlattice

-7\times 10^{-6}

A review on the flexural mode of graphene: lattice dynamics, thermal conduction, thermal expansion, elasticity and nanomechanical resonance.

K

First principle study of the thermal conductance in graphene nanoribbon with vacancy and substitutional silicon defects

^{-1}