Mooser, E. and Pearson

Mooser, E., and W. B. Pearson (1959). On the crystal chemistry of normal valence compounds. Acta Cryst. 12, 1015-22. 

The octet principle can be expressed as a formula by the generalized 8—N rule according to E. Mooser W. B. Pearson. We restrict our considerations to binary compounds, and presuppose the following ... 

Relative sizes of ions and the degree of covalence are important in determining structures of MX compounds. Mooser and Pearson plotted the average principal quantum number of the ions vs. the difference in electronegativites of the elements to give reasonable separation of CsCl, NaCl, ZnS (hep), and ZnS (ccp) structures. (E. Mooser and W.B. Pearson, Acta Crystallogy 1959 12 1015.) This plot is more successful than the radius ratio plots. 

A plot by Mooser and Pearson of average quantum number vs. difference in electronegativities of the M and X atoms was reasonably successful in separating CaF2, MX2 layer structures, Ti02 and Si02 (E, Moser and W.B. Pearson, Acta Crystallogy. 1959 12 1015.)... 

In addition to the reinterpretation of Pauling s rules developed by Burdett and McLarnan (1984), there have been a number of other studies related to various aspects of these standard rules. Due to the substantial number of errors in classifying AB compounds in terms of ionic radius ratio (e.g., Phillips, 1970 Tossell, 1980b), there have been numerous attempts to create structure maps that have two atomic quantities as coordinates and that can provide a unique separation of the different structure types. Such atom quantities may be related primarily to size or energy or to some combination of the two. Some of the most important such approaches are those of Mooser and Pearson (1959), Phillips (1970), and Simons and Bloch (1973). 

The inherent basis of these procedures is the Zintl-Klemm concept and the Mooser-Pearson extended (8 — N) rule. Formerly applied only to classical two-center-two-electron bonds, the extended procedures comprise all varieties of bonding (multiple bonds, partial bonds, multicenter systems, radicals, and free electrons). Generally, for a compound AmB , an electron transfer A- A +, B- mp = nq ) to the more electronegative element B forms pseudoelements k, B that show the structural principles of the corresponding isoelectronic elements with the whole spread of homoatomic bond types. Alternatively, one can derive from the number of valence electrons e and cb according to the equation otca + nee + k = 3n the term k = saa + Y. bb - e, which accounts for the... 

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