Alternant or Alternating Hydrocarbon

A type of interaction of a coordinatively unsaturated metal atom with the electron density of one or several bonds of the ligands. 

A sequence of computational instructions which yield a solution to a specific problem. Algorithms can be numerical or analytical, or can operate on nonnumerical data such as strings. One important aspect when selecting algorithms for larger problems is efficiency, especially the scaling of execution time with input data size, which is typically represented by an expression such as logn, or /iP-compiete worst case, 

A reaction that occurs on a single potential energy surface within the Born-Oppenheimer approximation. 

A bound system of molecules stabilized by noncovalent inter actions (e.g., electrostatic). Synonymous with cluster. 

The arrangement of two or more molecules in agreement with similarities in their structures or physicochemical properties. The goal is to overlay similar regions (e.g., benzene rings) in several structures. See Pharmacophore and Drug Discovery. 

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