My research can be summarized in the following figure:
- Force field development
- Advanced Molecular Dynamics and Monte Carlo techniques
- Thermodynamics and Statistical Physics
I develop accurate force fields that mimic the quantum mechanical behaviour of the system. This is achieved by fitting force fields to reproduce the ab initio geometry and Hessian in equilibrium. The research resulted in a program (QuickFF) to quickly derive accurate force fields from ab initio input.
The force fields are then used in Molecular Dynamics (MD) and Monte Carlo (MC) simulations to generate trajectories that efficiently sample the phase space of the system. Depending on the molecular properties we are interested in, more advance ensembles and techniques are required.
Once we dispose of trajectories that efficiently sample the phase space, we can use them to compute several thermodynamic properties such as thermal energy, entropy, heat capacity, equilibrium volume, ... Calculating the entropy is not straightforward and requires advanced MD techniques such as thermodynamic integration, free energy perturbation, metadynamics, ... I also develop (semi-)analytical models that can easily transform the computed input data between different ensembles. As such, we are able to constraint the system to satisfy realistic experimental conditions.
Most of my research is applied to Metal-Organic Frameworks (MOFs), which are a relatively recent class of hybrid materials consisting of inorganic metal clusters connected to each other by means of organic linkers. This results in periodic frameworks (crystals) with pores of several nanometers (nanoporous). MOFs have some very attractive applications such as detection, separation and detection of gasses, catalysis of chemical reactions, nanosprings and nano shock absorbers, drug delivery system, ... . Furthermore, some of these MOFs are very flexible and can expand or shrink under influence of external stimuli such as mechanical pressure, temperature, adsorption of guest molecules, ... this phenomenon is called breathing. To describe this breathing on a large scale, one requires accurate force fields to generate the microscopic data and one also requires thermodynamic models to impose realistic working conditions.