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Vibrational spectroscopy of selected molecular crystals

Mercredi 4 décembre 2013 11:00 - Duree : 1 heure
Lieu : Seminar Room, ILL4 - 6 rue Jules Horowitz - Grenoble

Orateur : Kacper DRUZBICKI (Department of Chemical Physics, Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060, Cracow, Poland. Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, 141980 Dubna, Russia)

Although the numerical theoretical computations have become a well established tool in solid-state lattice dynamics physics, the biggest impact has been always given to Inelastic Neutron Spectroscopy (INS), while the theoretical optical vibrational spectra were not so straightforward to be explored. Plane-wave formulation of Density Functional Theory (DFT) is the first-choice method, delivering an excellent compromise between the accuracy and computational cost. Density Functional Perturbation Theory (DFTP) has recently become the state of the art approach for studying the vibrational dynamics of condensed matter, pushing out the limits of static quasi-harmonic approach and making the optical-vibrational spectroscopy computations feasible. An extensive validation of DFPT method in prediction of solid-state vibrational spectra of selected complex molecular systems has been given here. The plane-wave generalized gradient approximation (GGA) of density functional theory has been widely tested with high numerical accuracy. Multiple exchange-correlation functionals in combination with norm-conserving pseudopotentials were probed along with semiempirical corrections for the dispersion forces. The computations support the manifold of experimental work performed for plenty of different systems. Infrared, Raman, Terahertz as well as INS spectra are reported for multiple solids - including ferroelectric liquid crystals, metal-organic plastic crystals, photoinitiators for cationic polymerization, hydrogen-bonded systems and polymorphs, organic ferroelectrics or very large organic pharmaceutics. The critical view on the performance of the quoted theory in the prediction of the structural properties and vibrational spectra of molecular crystals has been drawn. The special impact has been given to optical vibrational spectroscopy, showing pros and cons of selected methodology.

Contact : zbiri@ill.fr

Discipline évènement : (Physique)
Entité organisatrice : (ILL)
Nature évènement : (Séminaire)
Evènement répétitif : (General ILL Seminar - College 7)
Site de l'évènement : Polygone scientifique

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