- © The Mineralogical Society Of America
Studies of bond lengths and angles and electron density distributions observed for earth materials and related molecules and those calculated with computational quantum chemical strategies have been a meeting place where experiment has engaged theory in advancing our understanding of bonded interactions. Not only have the calculations provided a physical basis for the proposal that the bond lengths and angles are governed in large part by short-ranged molecular-like forces, but they have also provided a connection between bond length, bond strength and the bond critical point properties of the electron density distributions. They have also provided a basis for Pauling’s (1929) famous definition of bond strength and for the Brown and Shannon (1970) proposal that bond strength can be used as a simple measure of bond character. In addition, extrema in the local charge concentration of the valence electrons of the oxide anion and the electron localization function of electron density distributions calculated for earth materials and related molecules were found to highlight features ascribed to lone-pair and bond-pair domains and to sites of potential chemical reactivity.
In this chapter, a number of properties will be examined including bond length and angle variations, bond strength, crystal and bonded radii, bond “stretching” and “bending” force constants, polyhedral compressibilities, molecular based potential ad hoc energy functions, the generation of new structure types for silica and the bond critical point properties of observed and calculated electron density distributions. Local concentrations and localizations in the distributions (sites of potential electrophilic attack) for several earth materials and related molecules will also be examined and compared.
BOND LENGTH AND BOND STRENGTH CONNECTIONS FOR OXIDE, FLUORIDE, NITRIDE, AND SULFIDE MOLECULAR AND CRYSTALLINE MATERIALS
Bond lengths and crystal radii
With the on-going invention and development since the 1950’s of sophisticated tools and important advances in computer power and software for collecting and processing X-ray, neutron and electron diffraction data and microwave and molecular beam spectra, thousands of structural analyses …