Energy, multiple minimum problem

For even small assemblages of molecules, such as dimers and trimers, the multiple minimum problem may arise. That is, there may be different ways that one can put the molecules together and obtain minimum energy structures. One will probably want to... 

Fig. 4. Multiple-minima problem a local minima, b absolute minimum, c global minimmn. The absolute minimum corresponds to a minimal enogy the global minimum corresponds to a minimal free energy (allowing for the entrcqn4...

The kind of information obtainable through the use of the isotopic perturbation method is manifold and the problems which can be investigated cover a broad range. Fundamental questions connected to the interplay between molecular dynamics and structure like the distinction between time-averaged symmetry of molecules with a multiple minimum energy... 

It is a simple matter to know you are at the bottom of a well—in a true energy minimum. But how can you be sure it is the lowest possible structure, the global minimum (Figure 2.25) In fact, you carmotbe sure. There is no general, reliable solution to the global minimum problem. Just because a geometry optimization has produced a stable structure does not mean that a more stable structure cannot be found. The molecular mechanics method is especially susceptible to this problem. The more complicated the system, the more likely there are multiple minima. 

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