Crystallization glass-forming liquids

D. W. Henderson, Thermal Analysis of Non-Isothermal Crystallization Kinetics in Glass Forming Liquids , Journal of Non-Crystalline Solids, 30 301-315 (1979). 

H. Yinnon and D. R. Uhlmann, Applications of Thermo-analytical Techniques to the Study of Crystallization Kinetics in Glass-Forming Liquids, Part I Theory , J. Non-Crystalline Solids, 54 301-315 (1983). 

At the onset of the ferroelectric phase transition the Cu+ ions are frozen and no longer constitute the seed of the relaxation process. In this respect the ferroelectric phase transition quenches the glass-forming liquid. Below the phase transition temperature, the dipolar clusters surrounding the Nbs+ ions merge to yield the spontaneous polarization of the (now ferroelectric) crystal, and due to the strong crystal field, the off-center potential minima of the Cu+ ions are no longer symmetrical. 

Thus, one may summarize the physical picture of the relaxation dynamics in KTN crystal-doped with Cu+ ions in the following way In the paraelectric phase, as the ferroelectric phase transition is approached, the Nb5+ ions form dipolar clusters around the randomly distributed Cu+ impurity ions. The interaction between these clusters gives rise to a cooperative behavior according to the AG theory of glass-forming liquids. At the ferroelectric phase transition the cooperative relaxation of the Cu+ ions is effectively frozen. ... 

One important point we should stress, in conjunction with our current interest, is that similar slow relaxation as liquid water is observed in much simpler model systems The binary mixture of Lennard-Jones liquids, which consist of two species of particles, is now studied extensively as a toy model of glass-forming liquids. It is simulated after careful preparation of simulation conditions to avoid crystallization. Also, the modified Lennard-Jones model glass, in which a many-body interaction potential is added to the standard pairwise Lennard-Jones potential, is also studied as a model system satisfying desired features. 

Relaxation functions for fractal random walks are fundamental in the kinetics of complex systems such as liquid crystals, amorphous semiconductors and polymers, glass forming liquids, and so on [73]. Relaxation in these systems may deviate considerably from the exponential (Debye) pattern. An important task in dielectric relaxation of complex systems is to extend [74,75] the Debye theory of relaxation of polar molecules to fractional dynamics, so that empirical decay functions for example, the stretched exponential of Williams and Watts [76] may be justified in terms of continuous-time random walks. 

Interestingly enough, if a glass-forming liquid were cooled slowly enough (at several times the age of the universe ) such that it follows the dotted line shown in Fig. 9.8Z) at a temperature T kau the entropy of the supercooled liquid would become lower than that of the crystal — a clearly untenable situation first pointed out by Kauzmann and referred to since as the Kauzmann paradox. This paradox is discussed in greater detail in Sec. 9.4.2. 

Tamaoki N, Aoki Y, Moriyama M, Kidowaki M. 2003. Photochemical phase transition and molecular realignment of glass forming liquid crystals containing cholesterol/ azobenzene dimesogenic compounds. Chem Mater 15(3) 719 726. 

TABLE 21.3 Crystallization Velocities and Viscosities of Glass-Forming Liquids ... 

V.A. Mallia, P.K. Vemula, G. John, A. Kumar, P.M. Ajayan, In situ synthesis and assembly of gold nanoparticles embedded in glass-forming liquid crystals. Angew. Chem. Int. Ed. 46, 3269-3274 (2007)... 

H. Shi, S.H. Chen, M.E. De Rosa, T.J. Running, W.W. Adams, Dynamic mechanical properties of cyclohexane-based glass-forming liquid crystals and a linear side-chain polymer analogue. Liq. Cryst. 20, 277-282 (1996)... 

S.H. Chen, J.C. Mastrangelo, T.N. Blanton, A. Bashir-Hashemi, Novel glass-forming liquid crystals. IV. Effects of central core and pendant group on vitrification and morphological stability. Liq. Ciyst 21, 683-694 (1996)... 

The coexistence of crystals and deeply supercooled liquids was suspected already one century ago for bulk systems [45]. More recently, the ice-water coexistence was reported by experiments, especially in the temperature range 140-21 OK [46-49], and by simulations in NML [50,51], evidencing the presence of 15-20% of liquid water between nanometer-sized icecrystals [50]. Notably, recent simulations concluded that in polycrystalline materials grain boundaries exhibit the dynamics of glass-forming liquids [52]. 

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