Calculating
vibrational frequencies of molecules
There
are several reasons for calculating vibrational frequencies of molecules,
including:
· Identifying
the nature of a stationary point found by geometry optimization (e.g. a minimum
or a saddlepoint)
· To calculate
the IR and Raman spectra of a molecule
· To calculate
thermodynamic properties of a molecule
Vibrational
frequencies are usually calculated by finding the normal modes of the molecule.
Each normal mode behaves like an independent harmonic oscillator.