Energy of the Crystal Lattice

Calculated from the formula of, S. Sarkisov [822], modified by O. I. Shulishova [823], 

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Comparing and Contrasting Nonionic compounds do not exist in crystal lattice structures but rather as individual particles, which are affected by other particles. In other words, nonionic compounds experience forces between particles. Based on what you learned in Part B about the melting points of ionic versus nonionic compounds, how do you think the attractive energy between particles compares with the energy of the crystal lattice ... 

Lattice Energy The energy of the crystal lattice of an ionic compound is the energy released when... 

The materials may be in a quasi-ionic phase when 1 > p > 0.5, or in a quasi-neutral phase when 0.5 > p > 0. In the simplest theoretical approach, the value of p depends on only three parameters D) the ionization potential of D Aa, the electron affinity of A and M, the electrostatic Madelung energy of the crystal lattice. A fully ionic lattice (p = 1) is then realized when /D - Aa > M, and a fully neutral lattice (p = 0) when /D — Aa < M. This result is, however, greatly obscured by the neglect of transfer integral t and of other relevant parameters [44]. 

In the simplest adiabatic case with an orbital singlet term, potential energy of the crystal lattice is parabolic with one minimum point. At low temperatures, vibrations of the lattice are localized at the bottom of this well, and as a rule, the so-called harmonic approximation applies. This corresponds to the so-called polaron effect and brings us to the concept of electrons coated with phonons. 

The dominant defect in silver halides is a Frenkel defect, in which a silver ion moves to an interstitial site. To calculate the energy required to form this defect we simply remove a silver ion from one position, put it in its new position and compare the energy of the crystal lattice with that of the perfect lattice. 

In a three-dimensional crystal lattice, 3 N waves propagate in three independent directions. The total kinetic energy of the crystal lattice consisting of N atoms of the same mass m can be found by the obvious formula. 

Calculation of energy of the crystal lattice and bulk modulus. 

It is difficult to prepare many of the compounds of the A° —systems by synthesis from the elemental components and alloys, because of the comparatively hi melting points of many binary materials (CdS, CdSe, ZnS, and others) or the incongruent ternary-phase melting. Therefore, to prepare new semiconducting compounds, it is sometimes advisable to use doubledecomposition reactions [16,17]. The thermal effect of these reactions, which is necessarily dependent on the direction of the exchange reaction, is calculated from the heats of formation or the energies of the crystal lattices. Various experimental results demonstrate the success of this approach [16]. An example is the preparation of lead metaselenoarsenite ... 

The values for the energy of the crystal lattice were calculated on the basis of the formula of E.S. Sarkisov [822], originally used by him for calculating the energies of crystal lattices of ionic compounds. The essence of Sarkisov s formula, however, derived on the assumption of the collectivization of electrons between the cores of atoms of the two components, makes it more suitable for calculation of the energy of the lattices of metal-like compounds with a high proportion of metallic bond this has been shown by G, V. Samsonov [457], O.I. Shulishova [823], and G, V. Samsonov and O. I, Shulishova [880],... 

In order to calculate the total bond energy of the crystal lattice we shall disintegrate the crystal in the following way ... 

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