Modelling Carbon Materials from Pencil and Paper to High-throughput Screening

Who: Johan Carlsson, Biovia, Cologne
Thursday, October 20, 2016 - 4:00pm to 5:00pm
Eberly Hall 307

Carbon materials have extraordinary properties, but utilizing these properties in applications requires a deep understanding of the materials. Modelling and simulations can here be a very useful complement to experiments and even be used to predict properties ahead of the experiments. This is particularly relevant for graphene, which was investigated theoretically in great detail long before it was possible to perform any experiments. The first investigations were performed on ideal sheets using pencil and paper, but as grown grown graphene sheets are often found to be polycrystalline. This talk will introduce the coincidence site lattice (CSL) theory to derive models of grain boundaries in graphene. A combination of force field and DFTB calculations showed that low energy grain boundaries can be described as an array of dislocations. The dislocation core introduce grain boundary states, which has implications on the electronic structure of graphene.
The extra ordinary properties of graphene and carbon nanotubes (CNT) may also be used to improve the properties of nanocomposites. This is an inherently multiscale problem, which required a combination of molecular dynamics and DFTB based electron transport calculations to understand the electron transmission across a CNT-junction in a composite. The calculations revealed that the electron transmission across the junction depend on the CNT-separation, but also on if polymer molecules entered into the region between the CNTs.
The properties of graphene can be changed and further optimized by doping. Introducing nitrogen into the graphene sheet increase the electron concentration in the material and large nitrogen content forms carbon-nitrides. A multiproperty screening methods has been able to predict the carbon nitride to be an metal-free alternative to photocatalysts for water splitting. This multiproperty screening approach can be extended to high-throughput screening of a large variety of materials.