Vacancy model

Ruby laser Ruby red glass Ruetschi vacancy model... 

The De Wolff disorder model has been extended to the cation vacancy model for /-Mn02 and -Mn02 by Ruetschi [42]. In this model the occurrence of manganese cation vacancies and the non stoichiometry of electrochemical Mn02 have been taken into account. Furthermore, the vacancy model deals with the explanation of the different water contents of manganese dioxide. Ruetschi makes some simple assumptions ... 

From the discussion of location of hydrogen and muonium in the lattice, it is clear that the bond-center position is the lowest-energy site in many semiconductors. In GaAs and Si, this site has only recently been experimentally associated with anomalous muonium, which is relatively immobile (Kief et al., 1987, 1988). The agreement between theoretical results for hyperfine parameters (Van de Walle, 1990) and experiment allows an unambiguous identification of Mu with the bond center. Other models, such as the vacancy model proposed by Sahoo etal. (1985, 1989), are no longer considered acceptable candidates for Mu. ... 

How does the change in lattice parameter of FeO with iron content corroborate the iron vacancy model and refute an oxide interstitial model ... 

Comparing these theoretical values with the experimental value, we again see that the evidence supports an iron vacancy model. 

K proved that the ground state of Vs0 corresponds to S = 1 and that the ZFS parameter D is positive. An anisotropic spectrum with S = was shown to confirm the isolated C vacancy model. The properties of sublimation grown semi-insulating SiC for device applications have also been studied19 by a wide range of techniques. 

Multiple-Charge-State Vacancy Model. On the basis of the previous discussion, diffusion depends upon the concentration of point defects, such as vacancies or self-interstitials, in the crystal. Therefore, diffusion coefficients can be manipulated by raising or lowering the concentration of point defects. 

For the calculation of the net adsorption enthalpies of transactinides on metal surfaces the partial molar enthalpies of solution and the enthalpy of displacement are required. These values can be obtained using the semi-empirical Miedema model [66-70] and the Volume-Vacancy or Surface-Vacancy model [32,70,71]. Data for these calculations are given in [34,72,73]. 

The lattice parameters of nonstoichiometric uranium oxides, quenched from 1100° C., were determined within the composition range U02 to U4Og. Two separate linear relations for the lattice parameter as a function of oxygen content were obtained one characteristic of U02+2. and the other of U409 J/. The two functions are a0 = 5.4705 - 0.094 x (0 < x < 0.125) and a0 = 5.4423 + 0.029 y (0 < y < 0.31). Helium displacement densities were determined for some samples the values obtained are consistent with an oxygen interstitial model for U02+a. and an oxygen vacancy model for U409 y ... 

The recombination of pairs of interstitials and vacancies has usually formed the basis of models for thermal annealing. It has sometimes been assumed that the vacancy is mobile (as in the vacancy model for self-diffusion) and sometimes that the vacancy is a fixed trap or sink, having a capacity of one interstitial atom, and the interstitial is mobile. The form of the kinetic equations is usually not dependent on the choice, and this is true even if both are mobile provided there is no initial correlation of interstitials and vacancies. 

The behaviour of 5 as a function of temperature can be derived from equation (7.53) by the same approach as in OCR model. Although functionally OCR and vacancy models are identical, there are important differences. Firstly, the assumptions such as multiple occupancy around NBO site, etc. made in the OCR model are absent in the vacancy model. Secondly, vacancy model avoids being specific to a moderately modified network glass. The vacancy model itself is rather relevant for discussion of ion migration, because, when an alkali ion in its stable position jumps out of it, the vacated site in principle causes both electrical and elastic... 

Paired vacancy model, for ionic transport in Pons, and his development of FTIR, 20... 

While Eq. (90) can be derived from a vacancy model of interdiffusion [9, 196-197] if off-diagonal Onsager coefficients are neglected [90,197] as well as from a dynamical version [192,198] of the RPA, after a long discussion in the literature [199-210] it has now become clear [204-209] that the dynamic coupling between composition fluctuations and stress in polymer blends needs to be considered for a proper description of interdiffusion. With reasonable assumptions one then can justify Eq. (91), see [208-210], While the experimental evidence is not entirely clear (see [211] for a review), the majority of experiments also seem to favor Eq. (91). 

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