Amir Farokh (PhD, Bernhardt Group, AIBN)

Title: Hydrogenated defected graphene as an anode material for sodium and calcium ion batteries

Selection of a suitable anode material plays an important role in achieving good performance and high electrical capacity of rechargeable batteries. Although sodium (Na) and calcium (Ca) offer some advantages over lithium (Li), they have larger atomic radii and therefore are not able to be used as a replacement for Li in graphite electrodes because of their inability to intercalate.  In this project, we have considered hydrogenated defected graphene materials to see if the hydrogenation can increase the loading and interlayer spacing of graphene. A material with one hydrogen atom on each dangling sp2/sp3 carbon atom in a mono-vacancy has been studied computationally. This material can be synthesized by passing controlled hydrogen gas stream over the defective graphene, which is assumed to contain uniformly distributed mono-vacancies. According to our computational results, a supercell of 6×6 hexagonal rings with four carbon vacancies (5.55%) and four hydrogen atoms (C68H4) can accommodate up to 16 Na or 16 Ca atoms, equivalent to 173.2 and 231.4 mAhg-1, respectively. Therefore, this material can be considered as a potential candidate for Na or Ca ion batteries.

Bertrand Caron (PhD, MD Group, SCMB)

Title: Improving the predictive ability of Empirical Force Fields using graph theory: A Big-Data approach

Computational methods can offer unique insight at an atomic level into the structure and dynamics of biomolecules. While ideally described quantum-mechanically, in practice simpler empirical “force field” descriptions are needed to describe inter-particle interactions. The predictive ability of any force field is only as good as the underlying model; and manual parametrisation is a tedious, error-prone and arbitrary process where parameters developed on a handful of compounds are transferred with little regard to the immediate bonded environment. The talk will focus on novel approaches using molecular graphs and large molecular datasets to simultaneously and consistently develop and refine parameters transferable to a wide range of compounds, with a systematic treatment of parameter interactions. Specifically, I will present two novel tools developed as part of collaboration with the CWI (VU, Amsterdam): OFraMP, an aided charge assignment graphical interface and FDB (Fragment DataBase), a repository of common fragments found in 12,000 molecules parametrised with a high-level of accuracy. Together, I will present how these tools can be used to develop parameters of near-QM fidelity for very big and complex structures such as dendrimers or large drugs. Ultimately, these parameters will be integrated as part of the Automated Topology Builder (ATB) web-server developed within the laboratory.