Inhomogeneous freezing

Fig. 102. Left Temperature dependence of the near ZF muon spin relaxation rate in i-Tb Mg,2Zn5(i on double logarithmic scales. The vertical dashed line indicates the onset of loss of asymmetry due to instnunental dead time. The inset shows the temperature dependence of power used in the power exponential fit to the relaxation spectra. The spin-glass temperature is near 8K. Right pSR asymmetry spectra of i-Gd Mg42Zn5o at 1.5 K, in the applied longitudinal fields shown. The solid lines are a least-squares fit of a mildly inhomogeneous freezing...

For systems where the bulk freezing transition is well understood, one may want to go one step further and investigate the modifications of the phase transition and the sohd phases in the event of external influence on the system. Flow does freezing happen in a confined situation where external boundaries are present What is freezing in porous media like A related question is What does the interface between sohd and liquid look like This is an intrinsic inhomogeneity that the system builds up by itself (if, as usual, the transition is first order). Let us describe some papers dealing with freezing under external influence. 

B. Laird, D. Kroll. Freezing of soft spheres a critical test for weighted density functional techniques. Phys Rev A 42 4810, 1990 D. Kroll, B. Laird. Comparison of weighted density functional theories for inhomogeneous liquids. Phys Rev A 42 4806, 1990. 

Two line narrowing techniques, matrix isolation and resonant laser excitation, are being used separately and in combination to eliminate inhomogeneous broadening (94). Microenvironmental inhomogeneities are reduced by freezing the sample into uniform site locations in isolation or Shpol skii matrices (95). Alternatively, with highly monochromatic and tunable lasers, it is possible to photoexcite only the subset of emitter sites in a low temperature matrix which have... 

Measurements of NMR for Ti, Ti [33], and Sr [34,35] were carried out for STO 16 and STO 18-96. Ti and Sr nuclear magnetic resonance spectra provide direct evidence for Ti disorder even in the cubic phase and show that the ferroelectric transition at Tc = 25 K occurs in two steps. Below 70 K, rhomb ohedral polar clusters are formed in the tetragonal matrix. These clusters subsequently grow in concentration, freeze out, and percolate, leading to an inhomogeneous ferroelectric state below Tc. This shows that the elusive ferroelectric transition in STO 18 is indeed connected with local symmetry lowering and impHes the existence of an order-disorder component in addition to the displacive soft mode [33-35]. Rhombohedral clusters, Ti disorder, and a two-component state are found in the so-called quantum paraelectric... 

The quantity (a/ )-1 acquires the meaning of effective temperature, which characterizes the energy properties of the surface. It is assumed that, when the catalyst is prepared, fluctuations occur in the distribution of atoms on the surface which in fact lead to its inhomogeneity later the fluctuations freeze, and the experimenter works with a well-defined, inhomogeneous, but immutable surface. 

Figure 2.23 Cross-sections showing the theoretical distribution of hydraulic head and gravity-induced groundwater flow pattern in two inhomogeneous drainage basins with laterally extensive hydrogeological units and a complex ground surface geometry (after Freeze and Witherspoon, 1967, Water Resources Researdi, Vol. 3, no. 2, Fig. 3, p. 628. Copyright by the American Geophysical Union).

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