Thermal conductivity of graphene nanoribbons under shear deformation: A molecular dynamics simulation

Abstract

Tensile strain and compress strain can greatly affect the thermal conductivity of graphene nanoribbons (GNRs). However, the effect of GNRs under shear strain, which is also one of the main strain effect, has not been studied systematically yet. In this work, we employ reverse nonequilibrium molecular dynamics (RNEMD) to the systematical study of the thermal conductivity of GNRs (with model size of 4 nm × 15 nm) under the shear strain. Our studies show that the thermal conductivity of GNRs is not sensitive to the shear strain, and the thermal conductivity decreases only 12-16% before the pristine structure is broken. Furthermore, the phonon frequency and the change of the micro-structure of GNRs, such as band angel and bond length, are analyzed to explore the tendency of thermal conductivity. The results show that the main influence of shear strain is on the in-plane phonon density of states (PDOS), whose G band (higher frequency peaks) moved to the low frequency, thus the thermal conductivity is decreased. The unique thermal properties of GNRs under shear strains suggest their great potentials for graphene nanodevices and great potentials in the thermal managements and thermoelectric applications.

Figure 1

(a,b) Atomic structure of graphene along armchair and zigzag direction under shear strain, where a₁, a₂ and a₃ is the bond angle, and A, B and C is the bond length, respectively. (c) The stress-strain curve of graphene under shear strain.

Figure 2. Typical example of temperature distribution which is induced by the heat flux J.

The initial setup of the RNEMD simulation of thermal conductivity. The temperature gradient is set as a function of atomic position along the nanoribbon’s axis,Y. The thermal conductivity of GNR is then computed accordingly based on the Muller-Plathe approach.

Figure 3

(a) Wrinkle structure of graphene under shear strain. (b) A side view of the graphene wrinkle, here the relation between the wavelength and amplitude: λ = h/2. (c,d) The relation curve of wavelength and amplitude to shear strain.

Figure 4. The change of the bond-angle and bond-length under shear strain.

The definition of the bond-angle and bond-length is in Fig. 1(a,b). Here, (a) is the shear bond-length in armchair and zigzag direction. (b) is the shear bond-angle in armchair and zigzag direction.

Figure 5. Thermal conductivity of graphene under shear strain.

Figure 6

(a,c) Are the phonon density of states (PDOS) as a function of frequency with strains from 0.05 to 0.20 for ZGNR. (b,d) Are the PDOS as a function of frequency with strains from 0.05 to 0.25 for AGNR.