Influence of dislocations in multilayer graphene stacks : A phase field crystal study

In this study, the influence of 5|7 dislocations in multilayer graphene stacks (up to six layers) is examined. The study is conducted using a recently developed phase-field crystal (PFC) model for multilayer systems incorporating out-of-plane deformations and parameterized to match to density functional theory calculations for graphene bilayers and other systems. The specific configuration considered consists of one monolayer containing four 5|7 dislocations (i.e., two dislocation dipoles) sandwiched between perfect graphene layers. This study reveals how the strain field from the dislocations in the defected layer leads to out-of-plane deformations, which in turn cause deformations of neighboring layers. Quantitative predictions are made for the defect-free energy of the multilayer stacks as compared to a defect-free system, which is shown to increase with the number of layers and system size. Furthermore, it is predicted that system defect energy saturates by roughly ten sheets in the stack, indicating the range of defect influence across the multilayer. Variations in stress field distribution and layer height profiles in different layers of the stack are also quantitatively identified.