The constriction widths of nine cases are 0.216, 0.648, 1.08, 1.512, 1.944, 2.376, 2.808, 3.24, and 3.672 nm, respectively. And four heat currents
(i.e., J = 0.2097, 0.3146, 0.4195, and 0.5243 μW) are performed for all the cases. The typical temperature profile of the graphene with nanosized constrictions is shown in Figure 2. As mentioned before, we produce an energy transfer from the sink region to the source region by exchanging the velocities. Selleck PF-6463922 Therefore, several additional phonon modes are excited, which leads to the temperature jumps near the high- and low-temperature slabs . Between those slabs and constrictions, the temperature BAY 11-7082 cost distribution is linear, but not completely symmetrical. Specifically, on the left side of the system, the mean temperature is 175 K and the thermal conductivity calculated by the Fourier law is 110 W/(m · K), while on the right side, the mean temperature is 125 K and a higher thermal conductivity, 133 W/(m · K), is obtained. The asymmetry shows the obvious temperature dependence of the thermal conductivity of graphene, which is consistent with the results AZD8931 cost confirmed by Balandin et al. on the aspects of first-principle calculations and experiments [1, 12]. Besides, in the following, we will mainly focus on the big temperature jump ∆T at the constriction as shown in Figure 2, which indicates that energy is blocked when passing through
the constriction and thus an additional thermal resistance is introduced. Figure 2 Typical temperature profile. The temperature profile is obtained by injecting the heat current of 0.5243 μW. The inset shows the corresponding simulation system with the constriction width of 1.512 nm. The temperature profiles of the systems with different-sized constrictions, under different heat current, are shown in Figure 3. And the insets show the dependence of the temperature
jump ∆T extracted from those temperature profiles on the heat current. As shown in Figure 3, with the heat current increasing, the temperature jump approximately increases Cepharanthine linearly, which indicates that the thermal resistance at the constrictions is an intrinsic property of the system and it is independent of the heat current, while for different systems, with a fixed heat current, the temperature jump varies with the constriction width. When the width is 1.08 nm, the temperature jump spans the range 25.5 to 63 K. But when the width is 1.512 nm, the range is from 18 to 42 K, one-third lower than the former. This thermal transport behavior is distinctly different from that of the bulk material, which is independent of the size, and indicates that the thermal resistance of constriction in graphene has obvious size effects. Figure 3 Temperature profiles versus heat current. (a, b) From different systems with the constriction widths of 1.08 and 1.512 nm, respectively.