Nano- and micro-mechanical analysis of flexoelectricity in graphene-based structures

Abstract

Graphene, a 2D material with exceptional electronic, mechanical, and thermal properties, has garnered significant interest for various applications. Flexoelectricity, a coupling between mechanical strain and electrical polarization, is a unique property of dielectric materials. This property can potentially revolutionize various fields, including energy harvesting, nanodevices, and sensors. However, understanding the flexoelectric behavior of graphene-based structures at the nano- and microscales is crucial for optimal utilization. Graphene is centrosymmetric, so it is not piezoelectric. To make graphene flexoelectric, bending or strain engineering can be applied. This study used the strain engineering method with different defects for polarization properties. GPAW, a Python-based software for Density functional theory (DFT), is used. Berry phase formulation is implemented to determine dipoles and polarization. The flexural rigidity of graphene is studied at the microscale level. In first-principles calculations, various electro-mechanical properties were determined. Polarization properties were evaluated using various defect geometries such as Stone-Wales and triangular defects in monolayer and multilayer cases. In the heterostructure case, the various combinations of Boron nitride nanosheets (BNNSs) and graphene layering patterns were studied for their polarization properties. The investigation delves into the intricate interactions at the nanoscale and microscale level, analyzing how flexoelectric properties manifest in graphene-based structures. The study aims to enhance our understanding of flexoelectric phenomena in graphene-based structures and their potential applications in advanced materials and devices by scrutinizing the electro-mechanical behavior at both nano and micro levels. Keywords: Graphene, Graphene nanoribbon, Boron nitride nanosheet, dipole, Berry phase, Polarization, Piezoelectricity, Flexoelectricity, Density functional theory, grid-based projector-augmented wave, Heterostructure, bandstructure, van der Waals forces, Quantum electrostatic heterostructure, Stone–Wales defects, graphenereinforced nanocomposite, Mechanics of materials.