Temperature dependence of thermal motion in crystalline naphthalene

Single-crystal data for naphthalene have been measured at five temperatures between 90 and 240 K. Positional and thermal parameters for C and H atoms at each temperature were refined by conventional least-squares techniques. The effect of varying the weighting scheme was examined. Contributions of internal molecular modes to the motions of the atoms turn out to be important. They were estimated for the C atoms at each temperature from a standard force field and subtracted from the experimental U~/ values. The corrected UiTs were then analysed to determine rigid-body translational and librational tensors for the naphthalene molecule. The absolute magnitudes and temperature dependence of these quantities have been compared with values calculated from atom-atom potentials and from spectroscopic data.