With “multiphysics modeling” we combine methods that have different physical content in order to obtain a more complete view of an applied problem. In materials science this can involve methods that bridge length and time scales; in length from atomistic to macroscopic levels through "electrons, atoms, grains and grids"; in time from femtosecond electron dynamics to slow processes perceived by humans. The combination can be obtained in terms of integrated algorithms or simply by piping datasets from one model to the other. Quantum mechanics is central in many such combinations in the description of optical properties as the microscopic light-matter interaction requires a quantum description. In the first part of my talk I will therefore describe some development in the quantum description of optical properties, in particular so-called response theory. Its implementation in the context of density functional theory, see e.g. [1], that is time-depdendent density functional theory, has been very successful in recent years in calculations of optical properties also of quite large systems. Such applications cover properties in a large wavelength region, from the X-ray region, over the optical and infrared regions and to the microwave and radiofrequency regions. In the later part of my talk I will bring up some contemporary research problems in optical non-linear phenomena where the multiphysics concept has been applied, like; design of materials for optical control, where the combination of of quantum mechanics (QM) and classical electrodynamics is applied [1]; the design of electro-optical switching materials through combination of QM and classical dynamics (QM and MD) [2]; studies of multiphoton induced light emission in quantum dots with QM coupled to statistical mechanics [3]; solvent effects on non-linear effects with polarizable continuum models [4], i.e. combining QM with dielectric theory.
1. Density-functional theory of linear and nonlinear time-dependent molecular properties, P. Salek, O. Vahtras, T. Helgaker, and H. Ågren, J. Chem. Phys. 117, 9630 (2002).
2. A quantum mechanical - electrodynamical approach to nonlinear properties: A. Baev, P. Welinder, R. Erlandsson, J. Henriksson, P. Norman and H. Ågren, J. of Nonlinear Optical Physics & Materials, 16, 157 (2007).
3. Electric field poled nonlinear optical systems, Y. Tu, Q. Zhang, and H. Ågren J. Phys. Chem. B 111, 3591 (2007)
4. Dynamics of multiple-photon optical processes in semiconductor quantum , Y. Fu, T.-T. Han, Y. Luo, and H. Ågren, J. Phys. Condens. Matter, 18, 9071 (2006).
5. Solvation of azide at the water surface: the Polarizable Continuum Model approach,
L. Bondesson, L. Frediani, H. Ågren, and B. Mennucci, J. Phys. Chem., 110, 11361 (2006).