MOLECULAR-DYNAMICS SIMULATION OF CRYSTALLINE IMIDAZOLE

A molecular dynamics (MD) simulation is performed on the hydrogen bonded crystal of imidazole at 293 K and 123 K in the rigid-body approximation to investigate the lattice dynamics through spectral properties. The potential is a pair potential obtained by fitting the lattice frequencies using a lattice dynamics (LD) calculation. Comparison between LD and MD shows that in the Raman spectrum the agreement is within a reasonable range but in MD the phonon density of states and the neutron scattering spectrum present peaks at frequencies well beyond the higher LD frequency. These peaks are showing up in the power spectrum of the autocorrelation function of the hydrogen bond. The latter becomes much shorter and the equilibrium structure is different from the LD structure. This is due to the hydrogen bond potential which is overbonding and which should be improved.