Mixed crystals of p-dichlorobenzene with p-bromchlorobenzene in the presence of vacancies in the structure

Polarization studies of low-frequency Raman spectra of solid solutions of p-dichlorobenzene with p-bromchlorobenzene (50% p-dichlorobenzene) were carried out. Analysis of the lattice vibration spectra of these mixed crystals shows that vacancies can be present in their structure. The presence of vacancies is responsible for the emergence of additional lines, including those in the 70 cm(-1) region. The calculation of the diffusion activation energy in a mixed crystal proves that its magnitude is determined by the spatial arrangement of p-bromchlorobenzene molecules in the lattice, their orientation relative to parahalides, and (to a lesser extent) temperature variations. (C) 2000 MAIK "Nauka/Interperiodica".