THERMODYNAMIC PROPERTIES AND PHASE-TRANSITIONS OF SOLID HYDROGEN HALIDES AND DEUTERIUM HALIDES

By analyzing the results of thermal measurements on solid hydrogen halides and deuterium halides described in the preceding papers, the vibrational properties and the mechanism of the phase transitions are discussed. From the low-temperature region, a number of properties have been derived, in particular, the apparent Debye characteristic temperatures at T = 0 and as a function of temperature, the enthalpies of sublimation at T = 0, the static lattice energies, and the energies required to reorient a molecule in the lowest phase III. In the region below the triple point the enthalpies of vacancy formation have been obtained. In the transition region the configurational heat capacities have been separated and the thermodynamic properties of the transitions have been derived. The existence of local order in phase I and the peculiar behavior of the disordering process in the chlorides have been suggested. The mechanisms of phase transitions have been correlated with the molecular interactions. © 1978.