Hydrogen protonic model

The critical hydrogen content for the ductility loss increased with increasing hydrogen solubility in the alloy. The fracture surfaces were not characteristic of those found under conditions of SCC. In terms of hydrogen and deuterium solubility in a similar series of bcc alloys, the equilibrium constants were determined at infinite dilution as a function of temperature The free energy function was expressed in terms of the bound-proton model. 

The hydrogen bond model described above could certainly be accepted only after obtaining quantitative mathematical evidence confirmed by experimental results (for vibrational frequencies). Broad generalisation and qualitative conclusions, such as the establishment of the connection between hydrogen bond formation and proton transition processes [5] could be arrived at only after such a quantitative corroboration. 

Keywords nanostructure, aquatic ion of hydrogen, proton conduction, computational chemistry, modeling... 

Miyazawa et al. (92) related rates of decrease of aliphatic hydrogen protons during pyrolysis of ethylene tar pitch to formation of mesophase. Yokono et al, (93) used the model compound anthracene to monitor the availability of transferable hydrogen. Co-carboniza-tions of pitches with anthracene suggested that extents of formation of 9,10-dihydroanthracene could be correlated with size of optical texture. The method was then applied to the carbonization behaviour of hydrogenated ethylene tar pitch (94). This pitch, hydrogenated at 573 K, had a pronounced proton donor ability and produced, on carbonization, a coke of flow-type anisotropy compared with the coarse-grained mosaics (<10 ym dia) of coke from untreated pitch. 

Metallic hydrides are usually nonstoichiometric compounds, as expected from their relatively low heats of formation and the mobility of hydrogen. They are ordinarily described, chemically, in terms of any of three models in which hydrogen is considered a small interstitial atom, a proton, or a hydride anion. These models are discussed critically with particular reference to the group V metal hydrides. The interstitial atom model is shown to be useful crystallographically, the protonic model is questioned, and the hydridic model is shown to be the most useful at present. The effect of hydrogen content on the lattice parameter of VHn and the structural and magnetic properties of several hydrides are discussed in terms of these models. 

Molecular-Level Modeling of the Structure and Proton Transport within the Membrane Electrode Assembly of Hydrogen Proton Exchange Membrane Fuel Cells... 

Fig. 9.12 Diagrammatic representations of the potential wells for the hydrogen atom in a H-bond as understood within the phonon assisted tunnelling model, shown above, and the independent proton model, below.

R.E. Lechner (2001). Solid State Ionics, 145, 167-177. Proton conduction mechanism in MjH(X04)2 crystals the trigonal asymmetric hydrogen bond model. 

For many of these hydrides there is still discussion whether properties such as magnetic susceptibility, electrical conductivity, etc., are best accounted for by a hydridic model with M"+ and H- ions, a protonic model where the hydrogen electrons are lost to conduction bands in the metal, or an alloy-like model without appreciable charge separation. 

Fig. 9.33. Mechanism of fragmentation upon ECD following the hot hydrogen atom model. Here, a protonated lysine residue captures the electron and immediately transfers a hydrogen atom to its neighboring carbonyl-O. Primary and secondary fragmentation pathways of the ions are shown. Adapted from Ref. [150] by permissioiL John Wiley Sons, 2004.

In a later paper Chouinard and Gustafson (1971) reported angular correlations of positron annihilation in erbium, gadolinium, holmium and ytterbium hydrides. The correlations were again claimed to be consistent with the predictions of the protonic model. Recent studies on yttrium dihydride (Sabin et al., 1972 Rozen-feld and Debowska, 1975) were interpreted on the basis of the proton model, but it was pointed out that the model fails for higher hydrogen concentrations, i.e. YH2-YH3 (Rozenfeld and Debowska, 1975). 

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