Phase transition and domain structure in iodoform crystals

Phase transition in an iodoform crystal has been established from the tempe rature dependence of the Raman spectra of "external" crystal vibrations at 260 K. The transformation mechanism is interpreted under the assumption on the existence in the crystal of domains where dipole moments of the molecul es have parallel or antiparallel orientations. Below the phase-transition t emperature, the structure is more ordered, and the crystal consists mainly of domains with the parallel orientation of dipole moments of the molecules , whereas above this point, the domains with the antiparallel orientation o f dipole moments prevail. The crystal as a whole is not a pyroelectric. (C) 2000 MAIK "Nauka/Interperiodica".