Mechanical failure of graphene and the anharmonic phonon coupling mechanisms

Abstract

Through ab initio molecular dynamics simulations, the mechanical failure of graphene under equibiaxial strains is studied and its failure strain is found to decrease with increasing temperature. Phonon spectra at elevated temperatures are calculated based on the third order interatomic force constants, demonstrating that the transverse optical mode (TO) at K point displays an intriguing waterfall behavior under large equibiaxial strains and its frequency decreases with increasing temperature. Moreover, the in-plane modes exhibit broader phonon spectra under large strains comparing to the out-of-plane modes, suggesting stronger in-plane phonon couplings and suppressed contributions to the lattice thermal transport. This work provides deeper insight into the long-standing conundrum for understanding the discrepancy between theory and experiment.