Temperature and pressure dependence of the Raman frequency shifts in anthracene

In this study, the Raman frequency shifts of phonons and vibrons of crystalline anthracene as functions of temperature (at zero pressure) and pressure (at ambient temperature) have been calculated using the experimental volume data from the literature. This calculation is performed for six phonons and nine vibrons through the mode Grüneisen parameters which have been determined from the Raman frequency and volume data at various pressures. Our predicted Raman frequencies of the phonon modes decrease with increasing temperature (zero pressure) linearly, whereas they increase with increasing pressure (ambient temperature) nonlinearly, as observed experimentally for anthracene. For vibrons, we find that the Raman frequencies are almost independent of temperature and pressure in this crystalline system. (author)