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To study the microdynamics of translational, orientational and vibrational motions in liquid N2O4, molecular dynamics simulations, including all degrees of freedom of vibrating N2O4 molecules, were carried out. Atom-atom Lennard-Jones potentials with and without Coulomb potentials (LJ + C and LJ, respectively), were adopted in the simulation. When Coulomb interaction between atoms was included, mean-squared force and torque increased, the velocity and angular momentum correlation functions decayed faster to more evident negative parts, and both the translational and orientational diffusion slowed down. Simulated rotational correlation functions for LJ + C agreed reasonably with those derived from Raman spectroscopy, while those for LJ were found to decay too fast. Vibrational correlation functions for the NN stretching v 3 mode were calculated and the vibrational spectra were obtained from their Fourier transforms. Two simulations for the harmonic and the anharmonic intramolecular potentials, where anharm...

The I.R. spectra of benzoic acid crystal composed of the A configuration were simulated using the method of molecular dynamics, where all degrees of freedom of vibration, rotation and translation were taken into account and the equilibrium charge and charge fluxes were employed in the formulation. The observed spectra were reproduced satisfactorily, and the crystal field effect considered in the simulation led to reasonable shifts of respective frequencies from those calculated by the normal coordinate analysis for an isolated dimer. The most remarkable shifts were observed in the OH stretching (ca. 200 cm−1) and the OH out-of-plane bending (61 cm−1) modes. Far infrared spectra were also obtained in the simulation. The compression of the O … O distance due to the crystal field effect was found to be between 0·04 and 0·05 A which agreed well with the experimental result.