Kapitza thermal resistance across individual grain boundaries in graphene

Abstract

We study heat transport across individual grain boundaries in suspended monolayer graphene using extensive classical molecular dynamics (MD) simulations. We construct bicrystalline graphene samples containing grain boundaries with symmetric tilt angles using the two-dimensional phase field crystal method and then relax the samples with MD. The corresponding Kapitza resistances are then computed using nonequilibrium MD simulations. We find that the Kapitza resistance depends strongly on the tilt angle and shows a clear correlation with the average density of defects in a given grain boundary, but is not strongly correlated with the grain boundary line tension. We also show that quantum effects are significant in quantitative determination of the Kapitza resistance by applying the mode-by-mode quantum correction to the classical MD data. The corrected data are in good agreement with quantum mechanical Landauer-Bütticker calculations.

Heat transport in pristine and polycrystalline single-layer hexagonal boron nitride

“…Their local temperatures are maintained at 310 K and 290 K, respectively, using a Nosé-Hoover chain thermostat [19] considering the conservation of momentum in the heat source and sink groups. One can also use a periodic boundary setup where the heat source and sink are separated by one half of the simulation cell length, but it has been found [27] that this is less efficient than the fixed boundary setup in obtaining the lengthconvergent Kapitza thermal resistance, because the periodic boundary setup effectively reduces [18] the system length by a factor of two. We have tested that using a simulation cell length of 200 nm is enough to obtain length-converged Kapitza thermal resistance for the h-BN grain boundaries.…”

“…The former shows a higher R most likely due to GBs composed of a mixture of three different dislocation types. The latter case corresponds to a well-known [9,27,38] high-symmetry boundary between tilted honeycomb lattices. Low R is due to a flat GB [27].…”

“…The latter case corresponds to a well-known [9,27,38] high-symmetry boundary between tilted honeycomb lattices. Low R is due to a flat GB [27]. For 2θ > 30 • , it is not clear what kind of behavior is to be expected.…”

“…Similarly to Ref. 27, we initialize the bicrystal PFC calculations with symmetrically tilted grains fitted to a periodic, two-dimensional computational unit cell whose dimensions are allowed to vary to minimize strain. The grain boundaries are initialized as sharp interfaces.…”

“…We consider the same tilt angles as in the previous work [27] for symmetric boundaries (SBs) in graphene. In addition, we also investigate the antisymmetric boundaries (ABs) where the two atomic species have been interchanged in just one of the two grains; compare Figs.…”