We compute the electron-phonon coupling (EPC) of selected phonon modes in graphene and graphite using various ab initio methods. The inclusion of nonlocal exchange-correlation effects within the $GW$ approach strongly renormalizes the square EPC of the ${\text{A}}_1^{\prime }$ $\mathbf{K}$ mode by almost 80% with respect to density-functional theory in the LDA and GGA approximations. Within GW, the phonon slope of the ${\text{A}}_1^{\prime }$ $\mathbf{K}$ mode is almost two times larger than in GGA and LDA, in agreement with phonon dispersions from inelastic x-ray scattering and Raman spectroscopy. The hybrid B3LYP functional overestimates the EPC at $\mathbf{K}$ by about 30%. Within the Hartree-Fock approximation, the graphene structure displays an instability under a distortion following the ${\text{A}}_1^{\prime }$ phonon at $\mathbf{K}$.

• Received 29 May 2008

DOI:https://doi.org/10.1103/PhysRevB.78.081406