Thermal conductivity of oxidized gamma-graphyne

Abstract

Graphyne is an allotrope of graphene containing both sp and sp 2 hybridized carbon atoms. In this paper, we perform non-equilibrium molecular dynamics simulations to explore the thermal conductivity of oxidized gama-graphyne based on the advanced reactive force field.The effects of the oxygen adsorption, its coverage and external tensile strain are thoroughly studied. Owing to the oxygen adsorption, the thermal transport property of gama-graphyne is greatly deteriorated with lower thermal conductivity. The thermal conductivity is controllable by altering the oxygen coverage as well as external tensile strain. The underlying mechanisms for the thermal conductivity change are elaborated by the corresponding vibrational density of states. Our simulation results imply that graphynes are more attractive than graphene in the thermoelectric applications where lower thermal conductivity is essential to achieve a higher figure of merit. Oxygenation and strain engineering are promising methods to modulate graphyne to achieve designated thermal properties.difference of a single substitution defect in a crystal. In the case of C 13 isotope defect, ‫ܯ߂‬ ‫ܯ‬ ⁄ = 1/12 . Similarly, the ‫ܯ߂‬ ‫ܯ‬ ⁄ of hydrogenized and oxidized graphynes can be estimated as 1/12 and 16/12. The oxidized graphyne has larger phonon scattering rate and 9 ܲ(߱) = ଵ √ଶగ ‫‬ ݁ ఠ௧ ൫∑ ‫ݒ‬ ே ୀଵ ‫ݒ)ݐ(‬ (0)൯݀‫ݐ‬ (2) As pointed out by Jing et al., 12 the phonon transport of graphyne is dominated by the longitudinal (heat flux direction) and flexural (out-of-plane) modes. The VDOS is calculated both in the heat flux direction (corresponding to x direction here) and out-of-plane direction.As shown in Fig. 4, the adsorption of O atoms on graphyne reduces the VDOS in the heat flux direction (Fig. 4a) and out-of-plane-direction (Fig. 4b) as compared with the pristine one.This reduction in the density of phonon modes reduces the specific heat of the phonon modes based on the Debye model for the specific heat of acoustic phonons 30 (specific heat ‫ܥ‬ ∝ ‫,)߱(ܦ‬ where ‫)߱(ܦ‬ is the VDOS for phonon mode i with frequency ߱ ), and thus reduces the thermal conductivity.

Dependence of Thermal Conductivity of Carbon Nanopeapods on Filling Ratios of Fullerene Molecules

“…To obtain more physical insight into the mechanism of filling ratio effects on the CNP thermal conductivity, the normalized vibrational density of states (VDOS) for CNP was calculated by performing a fast Fourier transform of the velocity autocorrelation function (VACF) , where ν is the phonon frequency, i the is imaginary unit, and the VACF can be calculated as where N is the number of carbon atoms, is the velocity of atom i at time t 0 , and the angular brackets indicate the ensemble average.…”

“…To obtain more physical insight into the mechanism of filling ratio effects on the CNP thermal conductivity, the normalized vibrational density of states (VDOS) for CNP was calculated by performing a fast Fourier transform of the velocity autocorrelation function (VACF) 39,40…”

Modeling and simulations for 2D materials: a ReaxFF perspective

“…(e) Schematics of the reverse non-equilibrium molecular dynamics simulation. Reproduced from [269] with permission from the Royal Society of Chemistry.…”

“…Buehler [267] to investigate also graphyne mechanical properties, and by Autreto and Galvao [268] to study the hydrogenation process of model graphyne membranes. Zhang et al [269] analyzed the thermal conductivity of an oxidized γ-graphyne via reverse nonequilibrium MD (figure 16…”

Spray-coated epoxy barrier films containing high aspect ratio functionalized graphene nanosheets

“…[13][14][15] Graphene and its derivatives have recently garnered signicant attention due to their excellent material characteristics, such as large aspect ratio, impermeability to gases, high electrical and thermal conductivity, good thermal stability with respect to most polymers, and availability for diverse chemical modication approaches. [16][17][18][19][20][21] Several approaches have been developed to prepare polymer/ graphene nanocomposites, and in many cases were found to exhibit not only greatly enhanced gas-barrier properties compared to polymers containing inorganic clays but also improved electrical and thermal conductivity when properly dispersed in a polymer matrix. 22,23 In addition to gas barrier applications, graphene-based materials could potentially be used as molecular gas lters, 24 metal protection layers to prevent corrosion, 25,26 effective surface lubricants, 27,28 and solvated ion separation membranes.…”