Studies of samples having undergone heat treatment

ATOMISTIC MODELS INVOLVING HIGH-TEMPERATURE STUDIES OF THE MICAS Studies of samples having undergone heat treatment 

Another approach is to examine how thermal behavior differs for apparently similar materials to deduce how the materials may differ (as in the case of smectite and illite, Tsipursky and Drits 1984 Drits et al. 1993). For these materials, single-crystal structural studies have not been attempted because the structures have considerable (stacking) disorder. Thus, thermal behavior was used initially to determine that some aspect of the structure, in this case cation or vacancy ordering, may differ for different samples of the same species. Powder X-ray diffraction was then used to confirm that these differences existed. 

Dehydroxylation, for example in muscovite, involves H2O loss, and not (OH) or H2 loss alone. Therefore, it is likely that the OH group that destabilizes initially must attract the H from the adjacent OH group following the reaction 2(0H) H20(t) + Or. The 

Kallai and Rozenson (1980) by Mossbauer analysis in Fe-containing muscovite and by Guggenheim et al. (1987) in the thermal analysis of muscovite and by MacKenzie et al. 

The PBS involves only approximate electrostatic relationships and it is not an accurate measure of bond strength in comparison to bond length. However, the anticipated movement of the A1 toward the Or atom will produce a stronger Al-Or bond based on the bond length and the simultaneous movement away from the oversaturated oxygen atoms produce weaker Al-0 bonds. 

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