  Very recently, a new graphene-like crystalline, hole-free, 2D-single-layer
carbon nitride C3N, has been fabricated by polymerization of
2,3-diaminophenazine and used to fabricate a field-effect transistor device
with an on-off current ratio reaching (Adv. Mater. 2017, 1605625). Heat
dissipation plays a vital role in its practical applications, and therefore the
thermal transport properties need to be explored urgently. In this paper, we
perform first-principles calculations combined with phonon Boltzmann transport
equation to investigate the phononic thermal transport properties of monolayer
C3N, and meanwhile, a comparison with graphene is given. Our calculated
intrinsic lattice thermal conductivity of C3N is 380 W/mK at room temperature,
which is one order of magnitude lower than that of graphene (3550 W/mK at 300
K), but is greatly higher than many other typical 2D materials. The underlying
mechanisms governing the thermal transport were thoroughly discussed and
compared to graphene, including group velocities, phonon relax time, the
contribution from phonon branches, phonon anharmonicity and size effect. The
fundamental physics understood from this study may shed light on further
studies of the newly fabricated 2D crystalline C3N sheets.
