Force field methods structurally different molecules

The picture of molecules being composed of structural units, functional groups , which behave similarly in different molecules forms the very basis of organic chemistry. The drawing of molecular structures where alphabetic letters represent atoms and lines represent bonds is used universally. Organic chemists often build ball and stick, or CPK space-filling, models of their molecules to examine their shapes Force, field methods are... 

Molecular mechanics simulations use the laws of classical physics to predict the structures and properties of molecules. Molecular mechanics methods are available in many computer programs, including MM3, HyperChem, Quanta, Sybyl, and Alchemy. There are many different molecular mechanics methods. Each one is characterized by its particular/orce eW. A force field has these components ... 

Most drug-like molecules adopt a number of conformations through rotations about bonds and/or inversions about atomic centers, giving the molecules a number of different three-dimensional (3D) shapes. To obtain different energy minimized structures using a force field, a conformational search technique must be combined with the local geometry optimization described in the previous section. Many such methods have been formulated, and they can be broadly classified as either systematic or stochastic algorithms. 

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