Determination of 4-Connected Framework Crystal Structures by Simulated Annealing Method

1 Determination of 4-Connected Framework Crystal Structures by Simulated Annealing Method 

The frameworks of molecular sieves are constructed from 4-connected TO4 tetrahedra. Deem and Newsam developed an approach to optimize an initially arbitrary T-atom configuration with respect to a cost function based on the T—T distances, T—T—T angles, and number of first-neighbor T-atoms, by simulated annealing using the Monte Carlo method.147,211 This method could be used to solve 4-connected crystal structures, as well as to predict unknown hypothetical structures. 

Examine visually the representations (projections down the three principal crystallographic directions) of the full unit-cell contents for each of the saved models, followed by addition of framework oxygen atoms between neighboring T-atoms, and DLS (Distance Least Squares) optimization. 

The simulated annealing method based on atom assembly can predict the theoretical structures of known and unknown frameworks. In general cases, urlK uc 6. 

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