Bonds in Solids

These non-local orbitals are the canonical MOs of the giant molecule. But we can always take linear combinations of the filled canonical MOs to produce an equivalent set of filled MOs which are localized. The elecron density and the energy are unchanged by this operation. The localized MOs are much easier to picture and to comprehend. Afterwards we will see how the delocalized MOs change the story. 

The LCAO-MO model used here is very similar to models already developed 

From the chemist s point of view, this is probably the most important property of a solid. It is defined as the energy required to dissociate one mole of solid into its constituent atoms  

We will write the cohesive energy as AEgxp since our immediate goal is to understand the experimental results already available from heats of formation of solids. We can ignore the small errors resulting from heats at 298 K rather than at absolute zero, the reference temperature for most theories. 

The cohesive energy tells us about the strength of the chemical bonds in the solid. Its magnitude determines the stability and chemical reactivity of AB. Eventually it is the quantity which determines the structure of AB, since different possible structures will have different energies. 

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If the field gradient has no axial symmetry, then a more complicated expression is found, involving an asymmetry parameter which is often moderate. In particular, the study of this parameter has been useful for the determination of resonance structures and for the understanding of the bonding in solid iodine. The contribution of each of the molecular electrons to q is given by a relation of the form... 

W.C. Hamilton and J.A. Ibers, Hydrogen Bonding in Solids, Benjamin, New York, 1968. 

Application of ligand field spectroscopy to problems of chemical bonding in solids. D. Reinen, Angew. Chem., Int. Ed. Engl., 1971,10, 901-909 (30). 

Bonding in solids may be described in terms of bands of molecular orbitals. In metals, the conduction bands are incompletely filled orbitals that allow electrons to flow. In insulators, the valence bands are full and the large band gap prevents the promotion of electrons to empty orbitals. 

Novack A (1974) Hydrogen Bonding in Solids. Correlation of Spectroscopic and Crystallographic Data. 18 177-216... 

Burdett, J.K. Chemical Bonding in Solids Oxford University Press, New York,... 

Hydrogen bonding in solid ice creates a three-dimensional network that puts each oxygen atom at the center of a distorted tetrahedron. Figure 11-16 shows that two arms of the tetrahedron are regular covalent O—H bonds, whereas the other two arms of the tetrahedron are hydrogen bonds to two different water molecules. 

As described in Section 10-, the bonding in solid metals comes from electrons in highly delocalized valence orbitals. There are so many such orbitals that they form energy bands, giving the valence electrons high mobility. Consequently, each metal atom can be viewed as a cation embedded in a sea of mobile valence electrons. The properties of metals can be explained on the basis of this picture. Section 10- describes the most obvious of these properties, electrical conductivity. 

Probing Hydrogen Bonding in Solids Using Solid State NMR Spectroscopy A. E. Aliev K. D. M. Harris... 

Aliev AE, Harris KDM (2004) Probing Hydrogen Bonding in Solids Using State NMR Spectroscopy 108 1-54... 

Molecular Orbital Theory and Chemical Bonding in Solids... 

MOLECULAR ORBITAL THEORY AND CHEMICAL BONDING IN SOLIDS... 

The bonding in solids is similar to that in molecules except that the gap in the bonding energy spectrum is the minimum energy band gap. By analogy with molecules, the chemical hardness for covalent solids equals half the band gap. For metals there is no gap, but in the special case of the alkali metals, the electron affinity is very small, so the hardness is half the ionization energy. 

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