Chemical softness

We note finally fhaf fhe development of multilayer, band gap systems with variable width by (electro)chemical soft preparation methods provides opportunities for low-cost structures with high efficiency in solar cell devices. Examples of such devices are given elsewhere in this book. 

Although we have concentrated in this chapter on the derivatives of the energy and density, there are other chemically meaningful concepts that can be derived from the ones presented here 144 161. Among these, the chemical softness, the inverse of the chemical hardness, and the local softness [47,48] have proven to be quite useful to explain intermolecular reactivity trends. 

Its inverse 5 = is naturally called chemical softness. The approximate expression... 

There is no obvious reason why oA should express Pearson s scale of softness. Nevertheless, it is evident that it succeeds much better than for instance the molar polarizabilities a given in Table 2. The border-line cases between hard and soft central atoms have aA around 3 eV, whereas typical hard behaviour is found when oA is below 2 eV. A mild criticism is that oA has a tendency to increase more with the oxidation number z than appropriate for the chemical softness, producing aA =... 

Williams MW, Hoeschele JD, Turner JE, et al. 1982. Chemical softness and acute metal toxicity in mice and Drosophila. Toxicol Appl Pharmacol 63 461-469. 

Fig. 2. The chemical softness may be connected with only small energy differences between empty and occupied orbitals. Hence, Mn(I) should be soft because of adjacent 4s and 3d orbitals of the central atom, and Mn(VII) should be soft because of adjacent 3d central atom and p ligand orbitals, whereas Mn(II) and Mn(III) with a fairly isolated, partly filled 3d shell are expected to be hard.

The general chemistry of nitrogen donors classify them as donors of intermediate properties, considerably softer than the oxygen donors, as has already been stated. The connexion between chemical softness and thermodynamics so far found to be valid thus demands that both AH0 and dS° should be markedly lower for the formation of complexes by nitrogen than by oxygen donors. The data for complexes formed by ammonia and ethylenediamine presented in Tables 5 and 6, will show that this is true. 

Chemical Softness type Lubricity Hydro- philicity Substantivity Stability to yellowing Non- foaming... 

Using less chemicals Soft hand through treatment in a tumbler or with enzymes and bionic finishes, with fluorocarbon polymers and dendrimers causing high fluorine efficiency by self organised layered structures... 

As a consequence, for an open system, the number of electrons and the density depend on p and v(r). The sensitivities of N and p(r) correspond to the second derivatives of the grand potential, and they are the chemical softness,7... 

An interesting feature of the Parr-Chattaraj proof of the Principle of Maximum Hardness, is that the specific example of chemical softness is not introduced until the last step. The proof should then be valid for many other observables, provided that certain restrictions are met. One requirement is that the observable always has a positive value (or in some cases always a negative one). 

The ideas of chemical hardness and chemical softness are reviewed, with special emphasis on the research work done on these concepts at the University of North Carolina at Chapel Hill. 

Electrophilicity Long Range Chemical Softness Formulation.227... 

It can be defined the chemical softness kernels associated to the electronic system ... 

From this relation it is concluded that, the chemical softness and hardness nucleus for a considered electronic system are inverse measurements. The relation (4.189) can be written also on another localization level when it is multiplied with />(r"), the result it is then integrated upon r and the Eq. (4.184) is taking into consideration-one obtains ... 

In the second identity (4.196) it was practically introduced the definition of global chemical softness S, and can be further used in writing the relations... 

ANALYTICAL CHEMICAL SOFTNESS BY DENSITY AND APPLIED POTENTIAL... 

The expression (4.216) can be easily developed if is considered the chemical softness nucleus as being de(compose) (in) by a local contribution Z(r) and a nonlocal contribution of the t) e ... 

ELECTROPHILICITY LONG RANGE CHEMICAL SOFTNESS FORMULATION... 

Bohmian quantum theory charge waves chemical action chemical reactivity chemical softness... 

The major importance of the above four parameters is their relationship with the HSAB principle. Actually, through the plot of E versus for several liquids on a solid, one ean obtain indirectly the values of the chemical softness l/q from the slope of C/E, as represented by the following equation ... 

Factors influencing nucleophilicity have been discussed and summarized (14, 15). For Sn2(C) reactions Edwards and Pearson (14) have compiled a nucleophilic order RS > ArS > SjOf > (H2N)2CS > I > CN > SCN > OH > Nf > Br > ArO > Cl > C5H5N > AcO > H2O. They noted that polarizability is the dominant factor. Since polarizability is intrinsically associated with chemical softness of a species, parallelism exists between nucleophilic order and softness order. 

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