Minimization grid search

From this simplified analysis, a systematic search of other than the smallest molecules at a coarse increment would appear daunting. A hybrid approach with a coarse grid search followed by minimization has been successfully used to locate minima. There are a number of algorithmic improvements over the "brute force" approach that enhances the applicability of the systematic search itself To understand these improvements, some concepts need to be defined. First is the concept (110)of aggregate, a set of atoms whose relative positions are invariant to rotation of the T rotational degrees of freedom. n-Butane is divided into aggregates as an illustration (Fig. 3.4). 

In this contribution, a brief review will be presented of the techniques of conformational searching such as the systematic grid search, minimization schemes and molecular dynamics. Also discussed will be the relative merits and shortcomings of the various semi-empirical quantum mechanical approximations such as CNDO, MNDO, AMI, PM3 and PCH O. 

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