Charge transfer partial

Schmickler [236] recently discussed the iodide ion transfer reaction near the Pt(lOO) surfaces in some detail based on the Anderson-Newns model of chemisorption [237, 233]. Some of the model parameters used in this work were obtained from computer simulations [190, 230, 234]. Besides the study of Ref. 234, which is outlined in the remainder of this subsection, no other simulations using similar realistic molecular models have been performed. 

Sa is the electronic energy level of the adsorbate ion relative to the Fermi energy of the metal. The electronic interaction between ion and metal induces the broadening A of the adsorbate energy levels. A characterizes the strength of the ion-metal interaction and decays rapidly with the distance from the surface. and qi, are known from the ab initio calculations A was then calculated from Eq. (19) for different values of the distance of the ion from the surface, z. 

In a polar medium, the partial charge transfer depends on two additional contributions due to the ion-solvent and metal-solvent interactions. Following the theory of electrochemical adsorption by Schmickler [232], the adsorbate energy level in solution, e is given by 

The partial charge on the ion in vacuum, qi decreases substantially at small distances from the surface (Fig. 37). Ion hydration stabilizes the ionic charge and consequently the partial charge transfer from the ion to the surface is reduced. Substantial charge transfer in solution occurs only at distances smaller than 4.5 A from the surface. At larger distances, qh is almost equal to -1. At 4.5 A, however, the 

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E mass spectrum. Processes of the partial charge-transfer type ... 

Partial charge-exchange reaction. Synonymous with partial charge-transfer reaction. 

Partial charge-transfer reaction. An ion/neutral reaction that reduces the charge on a multiply charged reaction ion. 

Paraxanthine—see Xanthine, 1,7-dimethyl-Parent name nomenclature, 1, 35 Parham cycloalkylation in chroman synthesis, 3, 783 Paromomycins as pharmaceuticals, 1, 154 Partial charge transfer from donor to acceptor stacks, 1, 350 Pasteurellosis... 

Quantitatively, however, it is evident that directly measured A0 values are on average 0.2 to 0.3 eV higher than AX values. This shift in the potential scale has been discussed by Trasatti,31 34 who has attributed such a systematic difference to the different conditions of measurement (different temperatures, nonequivalence between thin water layers and bulk water, uncompensated partial charge transfer in UHV). For a more detailed discussion, the reader is referred to the original papers. 

Stricktly speaking the partial charge transfer parameter Xj which appears in the modified electrochemical Langmuir isotherm (6.36) or (6.41) is not a constant but may vary with 0j or IT. This because, in view of Eq. (6.31) Xj is given by ... 

Effect of partial electron transfer parameter Figure 6.23 depicts the effect of the value of the partial charge transfer parameter A,d for fixed XA(= 0.15) on the rate enhancement ratio p(=r/r0) for the four main types of promotional behaviour, i.e., electrophobic, electrophilic, volcano and inverted volcano. The main feature of the Figure is that it confirms in general the global mle... 

Figure 6.23. Effect of partial charge transfer coefficient XD on catalyst performance for fixed X.A depending on dimensionless potential n, (a) electrophobic, (b) electrophilic, (c) volcano-type, (d) inverted volcano-type.

Xa partial charge transfer coefficient of electron acceptor A... 

Carrier generators in molecular conductors have been associated for a long time to a partial charge transfer between the HOMO (or LUMO) electronic band and other chemical species. These systems are known as two-component molecular conductors. Tetrathiofulvalene derivatives are versatile systems for the formation of molecular organic conductors due to their electron donor capacity by transferring one u-electron from the HOMO orbital, and to their planar shape that promotes their stacking as a consequence of the n-n orbital overlap. The electronic properties of these salts are essentially determined by the packing pattern of the donor molecules which, in turn, depends on the counter-ion. 

Partial Charge Transfer Specific adsorption of ions is often attended by a partial transfer of their charge to the metal surface for instance, in the specific adsorption of cations M + on platinum... 

Opinions differ on the nature of the metal-adsorbed anion bond for specific adsorption. In all probability, a covalent bond similar to that formed in salts of the given ion with the cation of the electrode metal is not formed. The behaviour of sulphide ions on an ideal polarized mercury electrode provides evidence for this conclusion. Sulphide ions are adsorbed far more strongly than halide ions. The electrocapillary quantities (interfacial tension, differential capacity) change discontinuously at the potential at which HgS is formed. Thus, the bond of specifically adsorbed sulphide to mercury is different in nature from that in the HgS salt. Some authors have suggested that specific adsorption is a result of partial charge transfer between the adsorbed ions and the electrode. 

Concerning NO, Hadjiivanov [67] reported that the coordination of the NO molecule to a cationic site via the nitrogen atom is accompanied by a partial charge transfer from... 

Zhang Y, Lin H (2008) Hexible-boundary quantum-mechanical/molecular-mechanical calculations partial charge transfer between the quantum-mechanical and molecular-mechanical subsystems. J Chem Theory Comput 4(3) 414—425... 

The adsorption strength of anions on Au electrodes follows the sequence of C104 < S042- < Cl < Br < I. The strong specific adsorption of halide ions leads to a partial charge transfer between the adsorbate and the metal electrode [234]. 

The interpretation of the electrosorption valence is difficult. The following, somewhat naive argument shows that it involves both the distribution of the potential and the amount of charge transferred during the adsorption process. Suppose that an ion Sz is adsorbed and takes up A electrons in the process. A need not be an integer since there can be partial charge transfer (cf. Chapter 4). We can then write the adsorption reaction formally as ... 

As noted before, the partial charge transfer is not well defined. Nevertheless, let us suppose that we can treat Sz+X like a normal species. Its electrochemical potential is then ... 

Schultze and Koppitz [3] assume that g is typically of the order of 0.1 [see Eq. (18.12)]. Using this value, estimate the partial charge-transfer coefficient of the ions in Table 18.1. 

EQCM frequency of 20 Hz, which corresponds to a one-third monolayer of sulfate species adsorption/desorption. However, the electricity from the above cyclic voltammogram current is calculated to be about 1 x 10 C ctn i.e., 6 x 10 molecules cin" which is about one-tenth of a monolayer. This may indicate that sulfate adsorption on Au(lll) is associated with a partial charge transfer process. In Fig. 25b, an increase in EQCM frequency was observed as for (a), and a decrease in the frequency was observed at the Cu underpotential deposition region. The frequency change due to Cu underpotential deposition is determined to be 35 Hz,... 

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