Secondary Valence Lattices

Nuclear distances of atoms, valence angle, symmetry of molecules, all in the solid state. Molecular aggregates, directions of strongest secondary valences in the lattice... 

In graphite, the distances between adjacent atoms in the principal plane are 1.45 A, while perpendicular thereto the smallest distance amounts to 3.3 A. We have before us a lattice which coheres in two directions by normal primary valences and by secondary valences in the third direction... 

Proceeding from graphite, let us finally imagine a carbon lattice, which coheres in one direction through primary valences and in the two other directions by secondary valences. Such a structure is impossible from carbon atoms alone where tetrahedral valence holds, but we can conceive of its being realized, e.g. from a carbon chain of double bonds alone. Its density must lie, according to the distance law, between 0.8 and 1.1, according to the particular manner of separation between the chains. 

An examination of the experimental data confirms the accuracy of this theory, the principle of which is to be sought in the diflference between primary and secondary valences in organic compounds which, although schematic, has been proved by experiment. In clear contrast, the hetero-polar inorganic lattices extend over a considerably larger density range, because in them the polarization properties are effective in addition to spatial requirements and they produce more complicated conditions. 

These include, notably, the layer lattices which cohere in two directions by primary valences and in the third by secondary valences examples, which we shall later discuss in greater detail, are Cdl2, M0S2, Asis, talc, graphitic acid and siloxene. The anisotropy of the linkage type is very markedly expressed in them by the laminar habit and by the mechanical properties. To this type belong also reticulate filamentous lattices such as exist in vulcanized rubber and in numerous synthetic high polymers. 

The next step leads us to those compounds, discussed above, in which the lattice itself is formed in all three directions by secondary valence forces, but in which the lattice units are kept together by primary valences. We have here the large number of molecular lattices consisting of compact units, such as CI2, CH4, CeHe and we arrive finally at the inert gases in whose lattice-like structure only secondary valence forces participate. 

The Lattice Valency model describes a methodology based on the modification of bulk material-based RSFs (previously defined from associated reference materials), to allow for high sensitivity/detection limit quantification over interfacial region. This was put forward to account for the variability in atomic secondary ion intensities from minor and/or trace elements with the valence stale of atoms (cations) making up the substrate (Iltgen 1997). Although trends consistent with expectations are noted within the few publications available, this method does not account for sputter rate variations, nor the impact of any segregation processes, if active. 

The Lattice Valency model attempts to correct for these variations by, firstly, deriving the valency of the cations making up the lattice, and then, secondly, applying valency-specific RSFs to the respective secondary ion emissions. The cation... 

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