Order-disorder, polymorphism, and phase transformation in halogenobenzenes

Glassy Anomalies in the Low-Temperature Thermal Properties of a Minimally Disordered Crystalline Solid

“…In addition, spectroscopic measurements [42] revealed that, curiously enough, the root mean square torque acting on a librating molecule decreases with decreasing temperature despite a significant contraction of the crystal lattice. The pioneering study of Weiss highlighted the molecular pseudo-symmetry of the halogenobenzenes as the main cause for the subtle disorder [43] and some further studies accounted for that orientational disorder [44,45]. According to recent works [39,40], the constituent PCNB molecules exhibit remarkably large (temperatureindependent) atomic displacements giving rise to a highly distorted crystal structure.…”

On the Nature of the “Bleaching out” Process of the 35Cl NQR Signals in 1,2,3-Trichlorobenzene

“…This phenomenon, termed "bleaching out", is observed for many compounds and can be interpreted by 1) the formation of disorder in the crystal structure, as observed for some di-and hexasubstituted halogenobenzenes [1,2], 2) reorientational motions, 3) the formation and migration of lattice vacancies [3],…”