Prof. Dr. Luuk Visscher focuses on the development and application of multiscale and multilevel methods for the description of complex molecular systems.
Research
My research can be subdivided in three major themes that are briefly discussed below.
1. Subsystem Methods based on Density Functional Theory
In this programme we develop and apply subsystem approaches that connect various quantum and classical mechanical methods. Using density functional theory (DFT) as unifying theory, we work on methods in which local electronic properties are calculated with accurate coupled cluster methods while the electronic structure of the environment is treated using a DFT or approximate DFT approach. This not only speeds up calculations by orders of magnitudes but also keeps a local picture that facilitates the transfer of results to model hamiltonian approaches. This enables multiscale approaches to the modeling of complex systems for a wide range of research fields; examples are enzymatic catalysis, virtual screening of pharmaceutically active compouds and light harvesting, in which respectively reaction rates, binding affinities, and excitonic couplings are input for models used at higher length and time scales.
2. Reducing the time-to-solution of computational models
In this line of research I work closely with the in-house SCM company and computer scientists to improve upon the speed and numerical accuracy of DFT-based modeling. We have recently extended our python-based scripting environment for multiscale computational workflows to automatically exploit parallelism. This enables use of the relatively cheap resources available in computational grids.
To shorten the time spent in indivdual calculations we furthermore collaborate with Oak Ridge National Laboratory to develop algorithms that scale up to the thousands of processor core available in the next generation supercomputers. This is combined with the development of algorithms suitable for GPU-accelaration as they are found in both supercomputers as well as in desktop computers.
An exciting new research line in this field concerns the investigation of quantum chemistry algorithms that can be run on quantum computers. Here we consider composite methods in which an otherwise intractable electron correlation problem can be solved using a quantum computer, while the another part of the calculation is done using a conventional computer.
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