The vibrations of glyoxal, studied by 'Multimode', with a large amplitude motion, using an ab initio potential surface

The procedure 'Multimode' was introduced by Carter and Bowman [1998, J. chem. Phys., 108, 4397], to calculate the vibrations of polyatomic molecules using normal coordinates. Recently Carter and Handy have introduced an extension to 'Multimode' to include one large amplitude torsional vibration for molecules for which an analytical potential is available. This procedure is now extended to molecules for which ab initio potential data may be calculated. Glyoxal (CHOCHO) is studied using the density functional approach to generate the potential surface data. The full J = 0 vibrational spectra is presented.