Lattice-gas approach

To further demonstrate the power of the kinetic lattice gas approach we review briefly the work on precursor-mediated adsorption and desorption [60,61]. We consider an adsorbate in which, in addition to the most strongly bound chemisorbed (or physisorbed) adsorbed state, the adparticles can also be found in intrinsic or extrinsic precursor states. One introduces three sets of occupation numbers, , = 0 or 1, = 0 or 1, and /, = 0 or 1, depending... 

The miscibility gap will be described more accurately when a meanfield lattice gas approach is choosen [30], The mathematical form of the interaction function in all the above models may bring about a negative value for the effective interaction parameter, g, while all binary interactions by themselves are positive. The complexity of copolymer phase behaviour can be attributed to this peculiarity, like the miscibility-windows in mixtures of a copolymer with another homopolymer [37], or with a second copolymer [38,39]. 

Garcia Sanchez L., L. Di Pietro, and P. Germann. 1996. Lattice-gas approach to surface runoff after rain. Eur. J. Soil Sci. 47 453-162. 

A lattice-gas approach to ion-ion and ion-solvent interactions (treated via a quasi-chemical approach or Monte Carlo simulations). 

An alternative treatment of the first-order phase transitions has been snggested by Retter who has introduced the lattice-gas approach. The most striking feature of this approach is that it disregards completely the role of the solvent molecnles in the properties of the adsorbed layer. Thus, the adsorbed layer behaves as a two-dimensional lattice gas where the solute molecules are distributed over the sites of a regular lattice. 

The model has been used to describe the cathodic transition step observed in the C vs. E plots of 5-iodocytosine adsorption on a Hg electrode with good results.However, it is not clear whether these results are circumstantial or not, since there is not a systematic study of the model that will involve tests of the whole pit region as well as of the stable (gaseous) region. It seems that the problems with the lattice-gas approach are that... 

Note that the lattice-gas approach might be an acceptable treatment for adsorption on solid electrodes, see for example... 

Adsorption on solid electrodes of high hydrogen overpotential such as Bi, Pb, Tl, and Cd, approximates to that on the Hg electrode. In contrast, the adsorption of organic compounds on the metals of the Pt group is irreversible due to chemisorption. However, even in this case the adsorption may be treated using conventional techniques, usually based on the lattice gas approach. Here, we briefly present the latest and interesting work carried out by Vayenas group on the electrochemical promotion. 

Abstract A novel lattice-gas approach has been developed to model the effect of molecular interactions on dynamic interfacial structure and flows of liquid-vapor and liquid-liquid systems in microcapillaries, Within a mean-field approximation, discrete time evolution of species and momentum densities consists of alternating convective and diffusive steps subject to local conservation laws. Stick boundary conditions imposed during the convective step cause momentum transfer to lattice particles in contact... 

The lattice gas approach is valid within certain limits for typical metallic hydrides, binaries as well as ternaries. Deviation from this idealized picture indicates that metallic hydrides are not pure host-guest systems, but real chemical compounds. An important difference between the model of hydrogen as a lattice gas, liquid, or solid and real metal hydrides lies in the nature of the phase transitions. Whereas the crystallization of a material is a first-order transition according to Landau s theory, an order-disorder transition in a hydride can be of first or second order. The structural relationships between ordered and disordered phases of metal hydrides have been proven in many cases by crystallographic group-subgroup relationships, which suggests the possibility of second-order (continuous) phase transitions. However, in many cases hints for a transition of first order were found due to a surface contamination of the sample that kinetically hinders the transition to proceed. 

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