Oxides spatial inhomogeneity

Ertl, G. (1989). The oscillatory catalytic oxidation of carbon monoxide on platinum surfaces. In Spatial inhomogeneities and transient behaviour in chemical kinetics, (ed. P. Gray, G. Nicolis, F. Baras, P. Borckmans, and S. K. Scott), ch. 37, pp. 563—76. Manchester University Press. 

Lombardo and Bell (1991) reviewed stochastic models of the description of rate processes on the catalyst surface, such as adsorption, diffusion, desorption, and surface reaction, which make it possible to account for surface structure of crystallites, spatial inhomogeneities, and local fluctuations of concentrations. Comparison of dynamic MC and mean-field (effective) description of the problem of diffusion and reaction in zeolites has been made by Coppens et al. (1999). Gracia and Wolf (2004) present results of recent MC simulations of CO oxidation on Pt-supported catalysts. 

Here we apply general results of the previous section to calculations of oxygen vacancies induced magnetism in the incipient ferroelectrics. The main difference between binary oxides considered in Sect. 4.3.4 is temperature and size dependence of dielectric permittivity. To be specific, here we consider magnetism in the incipient ferroelectrics due to presence of the oxygen vacancies. As the permittivity in nanostructured incipient ferroelectrics is spatially inhomogeneous and temperature dependent, this would generate plethora of effects in the physical properties size and temperature dependencies. The calculations performed in Ref. [48] confirmed these statements. 

The Belousov-Zhabotinsky reaction scheme can also produce moving spatial inhomogeneities in unstirred solutions. Spatial waves develop as an oxidizing region advances into a region of low but finite bromide ion concentration that falls below a critical value. The autocatalytic production of bromous acid at the interface advances the wave faster than the diffusion of any other molecules proceeds (Field et al., 1972). 

---