Anomalous thermal conductance of graphyne under lower temperature

The thermal transport properties of graphyne are investigated via equilibrium molecular dynamics (EMD) simulations and non-equilibrium Green's function (NEGF) method. It is found that the room-temperature thermal conductivity of graphyne is 93% lower than that of graphene with a similar size and decreases steeply with increasing the number of acetylenic linkages, which agrees with the results obtained by NEGF method qualitatively. Lattice dynamics calculations reveal that these phenomena can be attributed to the reduction of both phonon group velocities and phonon lifetimes in graphyne at low-frequency region. However, when the temperature is less than 30 K, the thermal conductance of graphyne exceeds that of graphene. Moreover, the anomalous thermal conductance behavior is not sensitive to the system lateral size. The underlying mechanisms for such phenomena are elaborated by the normal mode analysis.