2. Multiscale modelling

The research of the Division has in the past taken steps in the direction of effective. low scaling. modelling, nowadays also general multiscale/multiphysics modelling. This has made it possible to increasingly assume an interdisciplinary character of the projects and to carry them out in common with other biologists and chemists. From having mainly focussed on method development we now also focus on applications. Our research has been considerably widened in scope and we are now engaged in photonics, electronics, catalysis, magnetism, nano-particle technology, X-ray and laser science, bioinorganic chemistry, protein dynamics, as explained also in the other sections. A common theme of this research is that materials properties are derived from chemical structure and dynamics. Applications cover molecular nano and bio materials in the life- and materials sciences. An emphasis is now put on hybrid density functional theory/molecular mechanics (DFT/MM) approaches, where a quantum mechanical (QM) region is treated at the DFT level and the surroundings at the molecular mechanics (MM) level. An additional continuum layer, typically described by means of polarizable continuum model (PCM) can be added to that. The full interaction between the layers is accounted for in the property calculations.

A related concept to multiscale modelling is multiphysics modelling which combines models with different physical content without directly referring to length or time scales. We apply this concept to obtain a more complete picture of structures and micro processes involved in making up for a particular macroscopic property. In particular, we have mixed quantum methods (time-dependent Schrödinger equation), electrodynamics (Maxwell's equations), statistical mechanics (Monte Carlo), dielectric theory (polarizable continuum models). The combinations, or mixing, are obtained in terms of integrated algorithms or simply by piping datasets from one model to the others. The multiphysics concept has been utilized in a variety of applications, for instance in the area of non-linear optical materials.

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