Lattice energy components

The possibility of measuring the Volta potential in the system metal-solid-state electrolyte and using the data obtained to determine ionic components of the free lattice energy has been shown in our papers. Earlier, Copeland and Seifert measured the Volta potential between Ag and solid AgNOj in the temperature range between 190 and 280 °C. They investigated the potential jump during the phase transition from solid to liquid salt. 

Definition Lattice energy is the energy released when one mole of a crystalline compound is assembled at a temperature of 0 K from its infinitely separated components. 

The extent of the ionization produced by a Lewis acid is dependent on the nature of the more inert solvent component as well as on the Lewis acid. A trityl bromide-stannic bromide complex of one to one stoichiometry exists in the form of orange-red crystals, obviously ionic. But as is. always the case with crystalline substances, lattice energy is a very important factor in determining the stability and no quantitative predictions can be made about the behaviour of the same substance in solution. Thus the trityl bromide-stannic bromide system dilute in benzene solution seems to consist largely of free trityl bromide, free stannic bromide, and only a small amount of ion pairs.187 There is not even any very considerable fraction of covalent tfityl bromide-stannic bromide complex in solution. The extent of ion pair and ion formation roughly parallels the dielectric constant of the solvents used (Table V). The more polar solvent either provides a... 

The lattice energy of an ionic crystal is the amount of energy required at absolute zero temperature to convert one mole of crystalline component into constituent ions in a gaseous state at infinite distance. It is composed of the various forms of energies, as shown above. The calculation is in fact somewhat more complex because of the presence of various ions of alternating charges in a regular tridimensional network. 

Table 5.12 reports a compilation of thermochemical data for the various olivine components (compound Zn2Si04 is fictitious, because it is never observed in nature in the condition of pure component in the olivine form). Besides standard state enthalpy of formation from the elements (2) = 298.15 K = 1 bar pure component), the table also lists the values of bulk lattice energy and its constituents (coulombic, repulsive, dispersive). Note that enthalpy of formation from elements at standard state may be derived directly from bulk lattice energy, through the Bom-Haber-Fayans thermochemical cycle (see section 1.13). 

Table 5.37 lists the various terms of the lattice energy of some clinopyroxene components. Data refer to the C2/c spatial group. Components Mg2Si206 and Fe2Si20g, which crystallize in Pljlc, must thus be considered fictitious. ... 

Here the first term represents the lattice stability components of the phase , the second term the Gibbs energy contribution arising from cluster calculations and the third term is the excess Gibbs energy expressed in the form of a standard Redlich-Kister polynomial (see Chapter 5). 

It is evident that the electrostatic interactions constitute a major component of the lattice energy of ionic crystals. According the treatment for NaF described above, the ratio of absolute values of the electrostatic and repulsive forces to the lattice energy is l l/n, where n is the Born coefficient. With n ff = 7.445 (Table... 

The reader may be confused by the suggestion that the empty hydrate lattice being distorted by the addition of guests. Yet the method is pragmatically justified because it would be impossible to measure the empty lattice energies for all possible combinations of hydrate components. So we simply use methane for si (or propane for sll, or methane + neohexane for sH) as a reference case. With these references, the deviation occurs because an empty methane lattice is not the same as an empty CO2 or xenon lattice, and thus we try to account for that by using this activity term. This point is further discussed in Section 5.1.6. 

Molecular inclusion is now known to involve factors such as the size and shape of the various component molecules or ions, their complementarity, inter-molecular forces of attraction and repulsion, directional forces and properties, and supramolecular synthons [3], all of which make their contribution to the overall lattice energy. 

The 4-bands of solid Ar and Ne have a similar two-component internal structure [6,19]. Each band of the bulk emission associated with the transitions i—and lPi >lSo consists of a high-energy component stemmed from A-STE in a regular lattice and a low-energy one which appears to be associated with structural defects. 

The lattice energy U of an ionic compound is defined as the energy required to convert one mole of crystalline solid into its component cations and anions in their thermodynamic standard states (non-interacting gaseous ions at standard temperature and pressure). It can be calculated using either the Born-Land6 equation... 

Ionic solids are only soluble in extremely polar solvents, due to dipole-dipole interactions between component ions and the solvent. Since the lattice energy of the crystal must be overcome in this process, the solvation of the ions (i.e., formation of [(H20) Na]+) represents a significant exothermic process that is the driving force for this to occur. 

In classical approaches, the lattice energy E, which is the difference between the total energy of the system and that of its component ions at infinity, is expanded into a sum of pair, triplet, etc terms ... 

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