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O: Fachverband Oberflächenphysik

O 79: Focus Session: Frontiers of Electronic-Structure Theory VI (joint session O/HL)

O 79.5: Vortrag

Donnerstag, 30. März 2023, 12:00–12:15, TRE Ma

Accurate prediction of vibrational spectra for solid state systems from ab initio molecular dynamics — •Ekin Esme Bas, Thomas Heine, and Dorothea Golze — Chair of Theoretical Chemistry, Technische Universität Dresden, 01062 Dresden, Germany

We present a highly accurate computational method to calculate vibrational spectra for solid state materials, primarily for covalent-organic frameworks (COFs). IR and Raman spectra are important tools that are frequently used for material characterization. However, the experimental spectra are often difficult to interpret without aid from theory. The computation of IR and Raman spectra is usually based on the harmonic approximation where molecular vibrations can be determined as normal modes from the second derivatives of the electronic energy with respect to the coordinates. Although this method is more straightforward and computationally less expensive, anharmonic modes cannot be captured. Thus, we employ an AIMD (ab initio molecular dynamics) based approach to include vibrational anharmonicities. Power, IR and Raman spectra can then be calculated via a Fourier transformation of the time correlation functions of velocities, dipole moments and polarizability tensors, respectively [1]. We discuss different approaches to compute dipole moments and polarizabilities. We present the power, IR and Raman spectra we calculated for COF-1, and we compare our AIMD based approach to the spectra obtained via harmonic approximation and experiment.

[1] M. Thomas, M. Brehm, R. Fligg, P. Vöhringer, B. Kirchner. Phys. Chem. Chem. Phys., 6608-6622, 5, 2013.