The alignment of graphene flakes by electric field: A molecular dynamics simulation study

Graphene, a two-dimensional carbon material with exceptional mechanical, thermal, and electrical properties, has widespread applications in industries ranging from electronics to biomedicine. External electric fields (EFs) have been shown to effectively align graphene flakes, enhancing their performance in coatings, nanocomposites, and anisotropic materials. While molecular dynamics simulations have extensively explored graphene's mechanical and thermal properties, as well as EF-induced alignment mechanisms, the role of solvent effects-particularly the influence of water's directional hydrogen-bonding network under EF-remains underexplored in rigid graphene systems. This work investigates how static EFs (SEFs), alternating EFs (AEFs), and circularly polarized EFs (CPEFs) influence the alignment of graphene flakes with varying sizes and shapes, focusing specifically on solvent-mediated effects. Our results show that the SEF and AEF can align graphene flakes such that their normal vectors point in the direction perpendicular to the EF, while the CPEF orients the flakes so that their normal vectors are perpendicular to the rotational plane of the CPEF. For symmetric flakes, a precessional behavior is observed, while for non-symmetric flakes, the principal axes rotate in sync with the CPEF, exhibiting a lag angle that depends on both the frequency of the CPEF and the aspect ratio of the flake. These findings contribute to a deeper understanding of EF-directed alignment in graphene and other rigid discotic molecules, offering valuable insights for applications in nanoelectronics, energy devices, and functional materials.