Comment on “First principles calculation of lattice thermal conductivity in mono- and bi-layer graphene” by B

In a recent preprint Kong et al, arXiv: 0902.0642v1 (2009) claimed to calculate the lattice thermal conductivity of single and bi-layer graphene „from first principles”. The main findings were that the Umklapp-limited thermal conductivity is only slightly higher than that of high-quality bulk graphite along the basal plane, and that it does not strongly depend on the number of atomic layers. Here we explain that the calculation of Kong et al used a truncation procedure with a “hidden” parameter, a cut-off frequency for the long-wavelength acoustic phonons, which essentially determined the final result. Unlike in bulk graphite, there is no physical justification for introducing the cut-off frequency for the long wavelength phonons in graphene. It leads to substantial underestimation of graphene‟s lattice thermal conductivity and a wrong conclusion about the dependence on the number of atomic layers. We outline the proper way for calculating the lattice thermal conductivity of graphene, which requires an introduction of other scattering mechanisms to avoid a logarithmic divergence of the thermal conductivity integral.  Web-site: http://ndl.ee.ucr.edu/ D.L. Nika, E.P. Pokatilov, A.A. Balandin and A.S. Askerov, Comment on “First principles calculation of lattice thermal conductivity...” 2 In a recent preprint Kong et al [1] performed the “first principle” calculation of the thermal conductivity of monoand bi-layer graphene and found that it is around 2200 W/mK at 300 K. The authors also concluded that it does not depend significantly on the number of layers. The calculation used the phonon dispersion and the phonon-mode dependent Gruneisen parameters qobtained with the help of QUANTUM-ESPRESSO package (where q is the phonon wave vector). Here we explain that in order to obtain a finite value for the thermal conductivity of graphene, which is limited only by the phonon Umklapp scattering, Kong et al [1] had to use a truncation procedure with a “hidden” parameter – the cut-off frequency for the long-wavelength acoustic phonons. The selection of this cut-off frequency, which was not described in the text, effectively determined the final result. The physical reasoning previously used for introducing such a cut-off frequency in bulk graphite is not valid for the single layer graphene. For these reasons, both conclusions of Kong et al [1] do not have any merit. Kong et al [1] limited their consideration to the three-phonon Umklapp scattering. For the scattering rate, 1/U, they used a simplified expression given by Klemens for the basal plane of bulk graphite [2]: