PhysSoSt1303020MeletovLO.fm

Abstract

Abstract-The Raman spectra of a naphthalene crystal have been measured at room temperature in the pres sure range up to 20 GPa. The pressure shift and Grüneisen parameters for intermolecular and intramolecular phonons have been determined. The maximum rate of the pressure shift for intermolecular phonons is 44 cm -1 /GPa, and the rate of the pressure shift for intramolecular phonons lies in the range from 1 to 11 cm ⎯1 /GPa for different modes. The pressure dependence of the phonon frequencies for direct and inverse pressure variations has a hysteresis in the pressure range from 2.5 to 16.5 GPa. It has been shown that the lin ear dependence of the intermolecular phonon frequency on the crystal density has a peculiarity, which indi cates a possible phase transition at a pressure of 3.5 GPa. The pressure dependence of intramolecular phonons related to the stretching vibrations of hydrogen atoms exhibits features that are characteristic of intermolecular phonons, which is associated with the influence of shortened distances between the hydrogen atoms of the neighboring molecules on the intermolecular interaction potential