Search

Graphene nanoribbons (GNRs) have been suggested as a promising material for its use as nanoelectromechanical reasonators for highly sensitive force, mass, and charge detection. Therefore the accurate determination of the size-dependent elastic properties of GNRs is desirable for the design of graphene-based nanoelectromechanical devices. In this study we determine the size-dependent Young’s modulus and carbon-carbon binding energy in a homologous series of GNRs, C4n2+6n+2H6n+4 (n=2–12), with the use of all electron first principles computations. An unexpected linearity between the binding energy and Young’s modulus is observed, making possible the prediction of the size-dependent Young’s modulus of GNRs through a single point energy calculation of the GNR ground state. A quantitative-structure-property relationship is derived, which correlates Young’s modulus to the total energy and the number of carbon atoms within the ribbon. In the limit of extended graphene sheets we determine the value of Young’s modulus to be 1.09 TPa, in excellent agreement with experimental estimates derived for graphite and suspended graphene sheets. [ABSTRACT FROM AUTHOR]

Continuum mechanics modeling of carbon nanotubes has long been an attractive issue, but how to reflect exactly the physics essential of the atomic bonds still remains to be a challenging problem. To capture the distinguishing in-plane σ-σ and out-of-plane σ-π bond angle bending rigidities of C[Single_Bond]C bonds in carbon nanotubes, an equivalent beam element with rectangular section is proposed and a corresponding frame structure model for a single-walled carbon nanotube (SWNT) is developed. By using the model, the five independent elastic moduli of SWNTs with arbitrary chirality and diameter are evaluated systematically. It is found that the elastic properties of the SWNTs are transversely isotropic when the tube diameter is small. The smaller the tube diameter is, the stronger the dependence of the elastic properties on the tube size and chirality is, while when the tube diameter is large enough, the SWNTs degenerate from transversely isotropic to isotropic and the elastic moduli tend to that of a graphite sheet. The present model can be incorporated into any standard finite element software directly, providing an extremely versatile and powerful tool for the study of nanostructures that beyond the computational capability of current atomistic approaches. [ABSTRACT FROM AUTHOR]

A strain k·p model is used to investigate lattice temperature dependence of the piezoresistivity of p-doped silicon nanobeams in the range of 100–600 K, based on the self-consistent solution to the coupled Schrödinger–Poisson equations. According to quasiharmonic approximation, an analytical semicontinuum atomistic lattice model is presented to describe the effect of size and temperature on elastic constants of the silicon nanobeam by using the anharmonic Keating model. The result presented here indicates the piezoresistive coefficient of the silicon nanobeam, which is dependent on quantum confinement effects, has a negative and nonlinear temperature coefficient. A quantitative comparison of the piezoresistive coefficients calculated with and without considering the elastic constant correction shows that it is crucial to incorporate the size-dependent elastic constant correction in order to quantify the piezoresistivity. [ABSTRACT FROM AUTHOR]