Accession Number : ADA017044

Title :   Crystal Structures of Ideal, Ordered Two-Layer Micas.

Descriptive Note : Environmental research papers,

Corporate Author : AIR FORCE CAMBRIDGE RESEARCH LABS HANSCOM AFB MASS

Personal Author(s) : Giese,Rossman F. , Jr

Report Date : 05 SEP 1975

Pagination or Media Count : 211

Abstract : In minerals exhibiting cation disorder, the variation in crystal structure environments can be studied by constructing model structures for all possible cation distributions. The model structures are constructed using known interatomic distances with the computer algorithm DLS (distance least squares). For two-layer mica polytypes, the number of possible ways of distributing Si and Al over the 16 tetrahedral sites is large: 1820 for Si/Al = 3 (as in muscovite) and 12,870 for Si/Al = 1 (as in margarite). It is not feasible to compute DLS structures for all these models, so both populations have been sampled on a random basis to provide 100 cases each for muscovite 2 M sub 1 and margarite 2 M sub 1.

Descriptors :   *Crystal structure, *Mica, X ray diffraction, Computer applications, Least squares method, Tables(Data)

Subject Categories : Geology, Geochemistry and Mineralogy
      Crystallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE