Diffusion model defect

A possible step in this direction can be made through use of earlier relaxation studies on other systems. Hunt and Powles,— when studying the proton relaxation in liquids and glasses, found the relaxation best described by a "defect-diffusion" model, in which a non-exponential correlation function corresponding to diffusion is Included together with the usual exponential function corresponding to rotational motion. The correlation function is taken as the product of the two independent reorientation pro-... 

House, J. E. (1980). Thermochim. Acta, 38, 59. The original description of the defect-diffusion model of how reactions in sohd coordination compounds take place. 

Reneker, D. H. and Mazur, J. (1982) Stochastic defect diffusion model for relaxation effects in crystalline polyethylene, Polymer, 23, 401-412. 

P. Bordewijk [1975] Defect-Diffusion Models of Dielectric Relaxation, Chem. Phys. Lett. 32, 592-596. 

An early attempt to describe effects of coupled motions in relaxing dipole orientations was the defect diffusion model of Glarum (58) in which it is assumed that a dipole relaxes to a randomorientation either by exponential decay or by arrival of a nearest defect which completely destroys the correlation existing just before it arrives assumed to be determined by a random walk or diffusion process in one dimension, but otherwise unspecified. With T as the rotational relaxation time and as the diffusional time use of the diffusion solution for the absorbing wall problem (59) gives the frequency domain relaxation function... 

The defect-diffusion models of Glarum (17) and Phillips, Barlow and Lamb (19) may be used for the a relaxation for the solutes shown in Table 2. These models give the following normalized relaxation functions... 

The data for the Kerr-effect and dielectric relaxations for the solutes of Table 1 and for TnBP suggest that the cooperative a-process occurring just above Tg involves many molecules, and their motions are Just like those of a system of enmeshing cogs. The fluctuation-relaxation model, where c(t) is described by a defect-diffusion model, rationalizes our observations. However, other models may also give the result Ki(t) = K2(t) e.g. the diffusional motions of a bond on a tetrahedral lattice (94). 

Perez, J. Defect diffusion model for volume and enthalpy recovery in amorphous polymers. Polymer 29(3), 483 89 (1988)... 

Component A implies anisotropic main-chain-group and, if applicable, side-group reorientations covering a restricted solid angle range of the interdipole vector (proton resonance) or the electric field gradient principal axis (deuteron resonance). As concerns the main-chain groups, it is mainly due to rotameric isomerism [126, 127] and may be interpreted even in terms of defect diffusion models [128]. 

An argument against the defect mediated diffusion model is the same one used earlier that is, there are not enough defects as determined by ESR (Brodsky and Title, 1969, 1976) or Deep Level Transient Spectroscopy measurements (Johnson, 1983) to account for the motion of all of the bonded hydrogen in a-Si H. This objection is removed if the floating bonds are 104-106 times more mobile than the hydrogen atoms. However, such highly mobile defects would rapidly self-annihilate via the process. 

The De Gennes method can be applied directly to Bueche s model without the defect diffusion formalism. Consider a chain with n main chain atoms, mean square end-to-end distance , and a large number of entanglement obstacles along its contour. For simplicity, suppose the number of main chain atoms between successive obstacles and the scalar distance between obstacles are... 

Point Defect Models of Diffusion in Silicon. Under conditions of thermal equilibrium, a Si crystal contains a certain equilibrium concentration of vacancies, C v°, and a certain equilibrium concentration of Si self-interstitials, Cz°. For diffusion models based on the vacancy, Cv° Cf and the coefficients of dopant diffusion and self-diffusion can be described by equation 27 (15)... 

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