Potential static

Bonaccorsi ct al. [204 defined for the first time the molecular electrostatic potential (MEP), wdicli is dearly tfie most important and most used property (Figure 2-125c. The clcctro.static potential helps to identify molecular regions that arc significant for the reactivity of compounds. Furthermore, the MEP is decisive for the formation of protein-ligand complexes. Detailed information is given in Ref [205]. 

Examine the models of am monia and pyridine on your Learning By Modeling CD Are the calculated charges on nitrogen consistent with their relative basicities What about their electro static potential maps ... 

FIGURE 2 4 Valence bond picture of bonding in H2 as illustrated by electro static potential maps The Is orbitals of two hydrogen atoms overlap to give an or bital that contains both elec trons of an H2 molecule... 

FIGURE 4 2 Electro static potential maps of methanol and chloro methane The electrostatic potential is most negative near oxygen in methanol and near chlorine in chloromethane The most positive region is near the O—H proton in methanol and near the methyl group in chloromethane... 

FIGURE 4 14 Electro static potential maps of methyl cation and ethyl cation The region of high est positive charge is more concentrated in CH3 and more spread out in CH3CH2 (The electrostatic potentials were mapped on the same scale in order to allow direct comparison )... 

FIGURE 6 4 Electro static potential maps of HCI and ethylene When the two react the interaction is between the electron rich site (red) of ethylene and electron poor region (blue) of HCI The electron rich region of ethylene is associ ated with the tt electrons of the double bond and H IS the electron poor atom of HCI... 

FIGURE 9 3 Electro static potential maps of eth yiene and acetylene The region of highest negative charge (red) is associated with the TT bonds and lies between the two carbons in both This electron rich re gion IS above and below the plane of the molecule in ethylene Because acetylene has two TT bonds a band of high electron density encir cles the molecule... 

FIGURE 12 4 Electro static potential map of sul fur tnoxide The region of greatest positive charge sur rounds sulfur... 

FIGURE 14 1 Electro static potential maps of (a) methyl fluoride and (b) methyllithium The electron distribution is reversed in the two compounds Carbon IS electron poor (blue) in methyl fluoride but electron rich (red) in methyllithium... 

Examine the electro r static potential map of butanoic acid on t Learning By Modeling and notice how much more in tense the blue color (positive charge) is on the OH hydro gen than on the hydrogens bonded to carbon... 

FIGURE 19 4 Electro static potential maps of (a) acetic acid and (b) acetate ion The negative charge (red) IS equally distributed between both oxygens of acetate ion The color range IS different for (a) and (b)... 

Compare the electro r-static potential maps of sodium lauryl sul 5 fate and sodium stearate on Learning By Modeling... 

The graphic that opened this chapter IS a molecular model of phenol that shows its planar structure and electro static potential... 

Learning By Model ing contains electro static potential maps of all the amino acids in this table... 

FIGURE 27 1 Electro static potential maps of the 20 common amino acids listed in Table 27 1 Each ammo acid is oriented so that Its side chain is in the upper left corner The side chains affect the shape and properties of the ammo acids... 

Use alternate solvent with reduced static potential Use conductive materials of construction Add antistatic agent to nonpolar solvent Check conductivity prior to feeding Use static dissipating linings if applicable... 

Control humidity in operating area (as humidity increases, static potential decreases)... 

The metal cluster will be modeled as an infinitely deep spherical potential well with the represented by an infinitely high spherical barrier. Let us place this barrier in the center of the spherical cluster to simplify the calculations. The simple Schrodinger equation, containing only the interaction of the electrons with the static potential and the kinetic energy term and neglecting any electron-electron interaction, can then be solved analytically, the solutions for the radial wave functions being linear combinations of spherical Bessel and Neumann functions. 

Electro.static potential map for para-nitroaniline shows negatively-charged regions (in red) and positively-charged regions (in blue). 

Seys, A. A. and van Haute, A. A., Pitting Potential Measurements by the Static Potential Band Method , Philipp. Geogr. J., 16, 107 (1972) C.A., 79, 99726g Pourbaix, M., Signilicance of Protection Potential in Pitting, Intergranular Corrosion and Stress-corrosion Cracking , J. Less-common Metals, 28, 51 (1972)... 

Seys, A. A. and Van Haute, A. A., Pitting Potential Measurements by Means of the Static Potential Band Method , Corrosion, 29, 329 (1973)... 

Figure 6. Static potential of / - Mn02 after heating in air between 100 and 400 °C. All the samples were heated at each temperature for 2 h and cooled quickly to 25 °C, The potential was measured in 1 mol L 1 KOH solution. Point "a" and b" are the values obtained with the P - Mn02 samples which were cooled slowly (allowing samples to reach room temperature overnight).

In the classical world (and biochemistry textbooks), transition state theory has been used extensively to model enzyme catalysis. The basic premise of transition state theory is that the reaction converting reactants (e.g. A-H + B) to products (e.g. A + B-H) is treated as a two-step reaction over a static potential energy barrier (Figure 2.1). In Figure 2.1, [A - H B] is the transition state, which can interconvert reversibly with the reactants (A-H-l-B). However, formation of the products (A + B-H) from the transition state is an irreversible step. 

Concept and Significance of Mixed Potential, Corrosive Potential and Static Potential... 

Mineral static potential or mineral electrode potential is an important parameter. It plays an important role in flotation. It has been demonstrated that the floatability of minerals has direct relation with electrode potential because the grinding-flotation system is similar to the multi-electrode reaction coupled system. Therefore, it is important to study the variance rules of the mineral electrode potential under different conditions. 

Figure 8.18 illustrates the polarization of the corrosion couple between galena and other minerals. Galena has low static potential in the three sulphide minerals. When it contacts with other media, they form the corrosion cell. Galena appears anode and cathode polarization occurs. When galena contacts with Fe medium, which has lower potential than galena, the result is contrary (see Fig. 8.9). 

To subtract the cation Mg + from its lattice position in the crystal and to bring it to the surface, we must work against the static potentials (coulombic plus repulsive plus dispersive) at the Mg site. In terms of energy, this work corresponds to half the lattice contribution of Mg + (in the Mg site of interest—i.e.. Ml or M2 see section 5.2) to the bulk static energy of the phase (see also section 1.12) ... 

An alternative way of calculating defect energies on the basis of static potentials is that outlined by Fumi and Tosi (1957) for alkali halides, in which the energy of the Schottky process is seen as an algebraic summation of three terms ... 

Applying equation 4.75, we obtain an enthalpy of formation of Schottky defects of 2.64 eV, which is somewhat higher than the value derived by Ottonello et al. (1990) with static potential calculations (see table 4.2) ... 

Whenever dilfusivity rates are not experimentally known and cannot be estimated by static potential calculations, approximate values can be obtained by empirical methods. The most popular of these methods establishes a linear relationship between the enthalpy of the Schottky process (and enthalpy of migration) and the melting temperature of the substance (expressed in K) ... 

---