Structural analysis, simulated annealing

Shen, M., Letiran, A., Xiao, Y., Golbraikh, A., Kohn, H., Tropsha, A. Quantitative structure-activity relationship analysis of functionalized amino acid anticonvulsant agents using k nearest neighbor and simulated annealing PLS methods./. Med. Chem. 2002, 45, 2811-2823. 

A successfid indexing of the powder diffraction pattern, which can often be done automatically, yields the unit cell dimensions and information on possible space groups. The chemical analysis and sorption data indicate the framework density, or number of tetrahedra per unit cell. The challenge is then to position these tetrahedra within the unit cell such that (1) they fully interconnect in a sensible manner and (2) the necessary analytical data are reproduced. These structural constraints are quantified in an energy expression and simulated annealing [33,34] is employed as the global optimization approach. 

In the recent years, sophisticated modeling tools have become available, such as the Cerius (8), where various modules aUow the analysis of crystallization, crystal growth, and material form characterization. In brief, this technique uses a simulated annealing and a rigid-body Rietveld refinement procedure, whereby the calculated and measured XRPD patterns are compared if they agree sufficiently, the structure is deemed to be solved. Other modules offered by Cerus include ... 

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