Structural and dynamical behavior of an azide anion in water from ab initio molecular dynamics calculations Original Research Article

The solvation of an azide anion in deuterated water has been investigated using density functional theory based Car–Parrinello molecular dynamics calculations. The first solvation shell of the anion was found to contain between five and six hydrogen bonded water molecules, compared to the six to seven waters found in analogous classical studies based on empirical potentials. The stretching modes of the azide ion in solution and in the gas phase are both red shifted by more than 10% compared to experiment. In agreement with inferences from experiment, the asymmetric ν3 mode of azide in solution relaxes on a picosecond time scale. The calculated solvent shift of this mode is about +80 cm−1, which is somewhat greater than the measured value of +57 cm−1.