Abstract
Grain boundary triple junctions are a key structural element in polycrystalline materials. They are involved in the formation of microstructures and can influence the mechanical and electronic properties of materials. In this work we study the structure and energetics of triple junctions in graphene using a multiscale modelling approach based on combining the phase field crystal approach with classical molecular dynamics simulations and quantum-mechanical density functional theory calculations. We focus on the atomic structure and formation energy of the triple junctions as a function of the misorientation between the adjacent grains. We find that the triple junctions in graphene consist mostly of five-fold and seven-fold carbon rings. Most importantly, in addition to positive triple junction formation energies we also find a significant number of orientations for which the formation energy is negative.
Highlights
We first use phase field crystal (PFC) models to initialise relaxed atomic configurations in 2D, which are mapped into atomic coordinates for further relaxation with classical MD and quantum-mechanical DFT calculations both in 2D and 3D
Our calculations show that there exist both positive and negative formation energies on the order of a few electronvolts. This energy scale is low compared to the formation energy of the grain boundaries, which dominates the total energy of the systems
We consistently find slightly negative formation energies for triple junctions with small-angle armchair grain boundaries, but no obvious trends beyond this
Summary
In this work we have employed an efficient multiscale protocol[24] to model the energetics and atomic structures of triple junctions in graphene. We first use phase field crystal (PFC) models to initialise relaxed atomic configurations in 2D, which are mapped into atomic coordinates for further relaxation with classical MD and quantum-mechanical DFT calculations both in 2D and 3D. We concentrate here on the formation energy of triple junctions as a function of the misorientation between the adjacent grains.
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