T. Hrenar(1), R. Mitric(2) and Z. Meic(1)

(1) Faculty of Science, University of Zagreb, Strossmayerov trg 14, HR-10000 Zagreb, Croatia

(2) Humboldt Universität zu Berlin, Institut für Chemie, Brook-Taylor-Str. 2 12489 Berlin

A calculation of vibrational spectra with semiempirical or ab initio force fields gives generally too high values for vibrational frequencies. However, the use of the density functional methods (DFT) reduces the need for correction of frequencies or the corresponding force constants. On the other hand, calculations of vibrational spectra by molecular dynamics methods do not demand such empirical corrections.

With the calculated ab initio force fields we have carried out Newtonian dynamics. From the time dependency of the dipole moment one can deduce information on infrared (IR) spectra of molecules. The described method is applied to benzaldehyde, which is a proper molecule due to its size and availability of experimental data. The obtained results will be presented and discussed.