THE USE OF MONTE-CARLO METHODS TO DETERMINE THE DISTRIBUTION OF AL AND SI CATIONS IN FRAMEWORK ALUMINOSILICATES FROM SI-29 MAS NMR DATA

A Monte Carlo method was developed to determine the distribution of Al and Si cations from Si-29 MAS NMR data for framework aluminosilicates . The method was used to analyze data obtained from Cs-exchanged leuci te in its high-temperature cubic phase and from cubic analcime samples . It was also used to determine the number of Al-O-Al linkages in cord ierite for different degrees of Al-Si order. The results for cordierit e were correlated with the calorimetric data of Carpenter et al. (1983 ) to estimate the energy for the reaction (Al-O-Al) + (Si-O-Si) --> 2( Al-O-Si) of similar to 40 kJ/mol.