Dielectric function of solids and order-disorder problem

An analysis of the temperature evolution of the dielectric response function, examined in the most wide frequency range (∼ 10−5 ÷ 1015 Hz), is considered to be a perspective for investigation of disordered solids. The principal role of correlations between the high- and low-frequency properties is emphasized. Formation of the dynamical glass-like behavior at low temperatures from the ferroelectric excitations is exemplified by the dielectric spectra evolution in the RDP-ADP and TlGaSe2-TlGaS2 mixed crystals.