Polarizable model of graphite and its applications to nanotechnology

Graphitic materials are of significant importance in the research and industrial community due to their tunable electrical conductivity, band gap, thermal property and high strength to mass ratio. They are used in battery or fuel cells as electrodes, refractory material, lubricant, in nuclear reactors, aerospace, water purification, steelmaking and bio-sensing. In this work we present a realistic, all-atom polarizable model of graphite with flexible dummy electrons (Figure 1) to model the polarizable nature of electron cloud in graphitic structures (graphene, graphite and carbon nanotubes) in a similar way to the approach which we have used in the past to describe image charge effects for ions approaching metal surfaces (https://doi.org/10.1038/s41467-018-03137-8). The models predict density, lattice parameters, surface energy, hydration energy, water contact angle and elastic constants within 1%, 1%, 5%, 5%, 5% and ~10 % respectively as per the Interface Force Field protocol. Additionally, the model also reproduces experimental and DFT data on binding energies and profiles for cations (Na⁺, Li⁺), anions (F^-, Cl^-, Br^-) and neutral molecules (water and amino acids). We also discuss correlation effects across a single graphene layer, discussing examples where a standing graphene layer or carbon nanotubes are immersed in electrolyte solutions. An accurate description of such systems is of key relevance to design improved materials and devices for water desalination and electric energy from salinity gradient in two different electrolyte solutions (blue energy).