Pyrophyllite dehydroxylation process by First Principles calculations

Computer simulations of cations order‐disorder in 2:1 dioctahedral phyllosilicates using cation‐exchange potentials and monte carlo methods

“…For these reasons, in many cases, to obtain good results in cation ordering studies, a combination of experimental methods with molecular modeling, force field, first principles, and/or simulation methods is necessary. [3] In micas, Herrero et al [4] and Palin et al, [5] by means of experimental and theoretical methods, found a high dispersion of IV Al 31 (prefix superindex in Roman number on the cation means the symmetry of the sheet: tetrahedral or octahedral sheet), which is in agreement with the Loewenstein rule of AlAl pair avoidance. Conversely, some variation was found in the cation distribution for the octahedral sheet of phyllosilicates.…”

“…with Al 31 in illite-smectite of shales with low Fe 31 content, but that Fe segregates from Al in Fe-rich samples. Grauby et al found that Al 31 and Fe 31 tend to mix rather than to segregate in some samples of synthesized smectites.…”

“…Conversely, some variation was found in the cation distribution for the octahedral sheet of phyllosilicates. A nonrandom distribution of cations was found in the octahedral sheet of celadonites, where the Al 31 and Fe 31 show a tendency to segregate. [6] Drits et al [7] studied cation ordering in celadonites, glauconites, and Fe-illites by diverse experimental techniques (IR, M€ ossbauer, and EXAFS spectroscopies) and simulations by probabilistic methods; they found a certain degree of short-range ordering.…”

“…Grauby et al found that Al 31 and Fe 31 tend to mix rather than to segregate in some samples of synthesized smectites. These results were opposed to the Muller et al observations, [10] where, in montmorillonites, Mg 21 and Fe 31 form clusters.…”

“…Grauby et al found that Al 31 and Fe 31 tend to mix rather than to segregate in some samples of synthesized smectites. These results were opposed to the Muller et al observations, [10] where, in montmorillonites, Mg 21 and Fe 31 form clusters. On the contrary, in the same minerals, a random distribution of Fe 31 in samples with high Fe content was found by Vantelon et al [11] Combining experimental results (FTIR and 27 Al NMR spectroscopy) with Reverse Monte Carlo (RMC) simulations on interstratified illite-smectite samples, a short-range ordering in the octahedral cations was found with a tendency of Fe 31 segregation and Mg 21 dispersion.…”