Glassy dynamics

Abstract

W e review dynami c processes i n supercooled liqui ds and glasses as studi ed by dielectri c spectroscopy. It i s the only experim ental techni que whi ch allows one to follow the tremendous slow-down of di OE usi ve motion of parti cles i n di sordered condensed matter over m ore than 18 decades in frequency or ti me. The di electri c techniques used are treated in detai l. As an i ntroducti on for non-speciali sts, the ti me and temperature evolution of the basi c spectral features associated with vari ous dynami c relaxation processes are di scussed in detai l. Among them are the structural relaxati on, the occurrence of fast processes and the boson peak. The relevance of these features for glass formation i s discussed. T he present arti cle may also serve as a review for recent experi mental and theoretical studi es on glassforming liqui ds.

Suppression ofβRelaxation in Vapor-Deposited Ultrastable Glasses

“…At sufficiently high temperatures, structural relaxation in a liquid is governed by a single process [1][2][3], whereas dynamics in supercooled liquids split into primary (α) and secondary (β) relaxations [1][2][3][4][5]. Below the glass transition temperature, T g , the α relaxation is frozen but the β relaxation persists in the glassy state, thus becoming the principle source of dynamics in glassy states.…”

Chemical influence on β-relaxations and the formation of molecule-like metallic glasses

“…S upercooled liquids and glasses display diverse relaxation dynamics [1][2][3][4][5][6] . In addition to the primary (a-) relaxations that are responsible for the viscous flow, a kind of secondary relaxation, called Johari-Goldstein or b-relaxation [7][8][9] , often exists at high frequencies or low temperatures.…”

Double Primary Relaxation in a Highly Anisotropic Orientational Glass-Former with Low-Dimensional Disorder

“…The glass state is obtained when, upon cooling or pressurizing fast enough to avoid the transition to the crystalline state, a liquid gradually freezes, into an amorphous phase in which the molecular motions are quenched while the structural disorder of the liquid is retained. [1][2][3][4] A glass-like dynamics may appear also when a translational long-range order exists. In fact, many molecular systems form phases which are characterized by translational order and at the same time by orientational disorder.…”

“…[5][6][7] The reorientational motions may freeze upon cooling or pressurizing, resulting in an orientational glass: OD phases therefore exhibits a phenomenology that is analogous to that of structural glass formers. 4,[8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] Due to the large number of degrees of freedom of its constituent molecules, molecular condensed-matter systems are characterized by a rich variety of dynamic processes and phases. In molecular materials forming structural or orientational glasses, the most important dynamics is the cooperative motion of the molecules, referred to as primary relaxation or α process, whose freezing marks the transition to the glass state.…”