A new paradigm for modeling: a virtual multifrequency spectrometer

The subtle interplay of several different effects still makes the interpretation and analysis of experimental spectra in terms of structural and dynamic characteristics a very challenging task. In this context theoretical studies can be very helpful and this is the reason behind the rapid evolution of computational spectroscopy from a highly specialized research field toward a versatile and widespread tool. However, in the case of electronic spectra (UV–vis, CD, photoelectron, X-ray, etc.) the most popular approach still relies on computation of vertical excitation energies, which are further convoluted to simulate line-shapes. Such a treatment completely neglects the effect of nuclear motions, despite the well-recognized notion that proper account of vibrational effects is often mandatory in order to interpret correctly experimental findings.

In this presentation I will sketch the most significant developments performed also in the framework of the ERC Advanced Grant DREAMS: 320951 “Development of a Research Environment for Advanced Modeling of Soft Matter.

From the one side, recent implementations of effective approaches rooted into both time-independent and time-dependent models, allow feasible yet reliable simulations of spectra line-shape, including vibronic contributions even for large systems. Moreover, integration into a general purpose computational chemistry package offers a fully automatic evaluation of one-photon electronic spectra, starting from several electronic models, ranging from fully QM descriptions to discrete/continuum QM/MM/PCM models.  Additionally, introduction of effective DFT models coupling a remarkable reliability in the computation of geometric, vibrational and electronic properties with a very favorable scaling with the number of electrons, allows reliable studies of compounds of biological or technological interest. Some specific examples will be sketched to illustrate our recent integrated approach.

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