# Aggregation of Graphene Flakes Under Electric Field: A Molecular Simulation Study

## TL;DR

This study uses simulations to show how electric fields influence the self-assembly of graphene flakes into different structures.

## Contribution

The novel contribution is the systematic investigation of how various electric field types affect the aggregation behavior of graphene flakes.

## Key findings

- Graphene flakes form globular structures without an electric field but align in stretched configurations under static electric fields.
- Alternating and circularly polarized electric fields lead to weaker alignment and rotating elongated aggregates, respectively.
- The stretched state is the most stable configuration under electric fields according to free energy analysis.

## Abstract

Graphene flakes, as two-dimensional materials, can self-assemble
under certain conditions and have wide-ranging applications in industries
from electronics to biomedicine due to their exceptional mechanical,
thermal, and electrical properties. Recent studies indicate that single
graphene flakes can be aligned by an external electric field (EF)
in polar solvents like water. However, how their self-assembly behavior
is influenced by the EF remains unclear. In this work, we use molecular
dynamics (MD) simulations to explore the self-assembly of graphene
flakes with different shapes and sizes under various EF conditions:
static EF (SEF), alternating EF (AEF), and circularly polarized EF
(CPEF). Our results reveal that different EF conditions significantly
impact the number of pairwise bindings between flakes and the average
size of the aggregates. In the absence of an EF, graphene flakes tend
to form globular, round-like structures. When an EF is applied, particularly
under SEF, the aggregates adopt a stretched configuration aligned
with the field’s direction, while AEF has a weaker alignment
ability than SEF. Under CPEF, elongated aggregates rotate, following
the field with a characteristic lag angle. Furthermore, while aggregates
can explore more configurations under CPEF, the two-dimensional free
energy landscape indicates that the stretched state is the most stable.
This work deepens our understanding of how EFs influence the self-assembly
of graphene flakes, potentially guiding future engineering applications
for controlling the aggregation of graphene and other discotic molecules.