University of Namur, Theoretical Chemistry Laboratory, Namur Institute of Structured Matter
The application of laser light on molecules and materials give rise to nonlinear optical effects like second and third harmonic generation. At the molecular scale, the nonlinear optical properties are defined by the equation describing the influence of external (static and dynamic) electric fields on the dipole moment. The induced dipole reads:
where 
, 
, and 
are the polarizability, first and the second hyperpolarizabilities. The course intends to survey methods to evaluate these hyperpolarizabilities, with the aim of providing tools to deduce structure-property relationships and of designing new compounds (for sensing devices, optical telecommunications, data storage). The following aspects will be tackled: i) analytical versus numerical (finite field) differentiation schemes, ii) electron correlation effects, iii)
reliability of exchange-correlation functionals, iv) frequency-dispersion effects, v) vibrational versus electronic hyperpolarizabilities, and vi) effects of the surrounding (in solution and in the solid state). As a last point, if time allows
methods to account for dynamic effects on the hyperpolarizabilities will be briefly sketched as well as relationships with experimental observations.
Keywords: Hyperpolarizabilities, response functions, finite field, frequency dispersion, electronic versus vibrational contributions
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Virtual Winter School on Computational Chemistry