Hide/Show Apps

Correlations between the spectroscopic parameters and the thermodynamic quantities for systems exhibiting phase transitions

Download
2005
Karaçalı, Hüseyin
We correlate in the first part of this study the specific heat and thermal expansivity to the temperature-and pressure-dependent frequency shifts, respectively, in ammonia solid I, solid II, hexagonal ice and ice close to their melting points. This is carried out for some fixed pressures for the two translational and one librational modes in ammonia solid I. By obtaining linear plots of specific heat and thermal expansivity against temperature-and pressure-dependent frequency shifts, the values of slope were deduced and compared with experimental values. The correlation between the thermal expansivity and frequency shifts was constructed in the ammonia solid II by calculating the Raman frequencies of the translational and the librational modes for some fixed pressures. Calculated values of slope were compared with experimental values. Temperature and pressure dependent frequency shifts of the translational modes in hexagonal and ice are correlated to the specific heat and the thermal expansivity, respectively. When the mode Grüneisen parameter depends on temperature and pressure, correlations among the specific heat, thermal expansivity and, temperature-and pressure-dependent frequency shifts, respectively, are reexamined in hexagonal ice. When the mode Grüneisen parameter depends on temperature, correlation between the specific heat and the frequency shifts is reexamined using translational modes in NH4Cl. In the second part of this study, we predict the damping constant for ammonium halides (NH4Cl and NH4Br) for zero pressure, and for the tricritical and second order phase transitions for a lattice mode of NH4Cl. Also, the observed Raman intensities of this mode are analyzed at those two pressures.