Molecular potential stationary point

Iti Chapter 1, we dealt at length with molecular mechanics. MM is a classical model where atoms are treated as composite but interacting particles. In the MM model, we assume a simple mutual potential energy for the particles making up a molecular system, and then look for stationary points on the potential energy surface. Minima correspond to equilibrium structures. 

Conducting reactions in nanospace where the dimensions of the reaction vessel are comparable to those of the reactants provides a new tool that can be used to control the selectivity of chemical transformations.1 This dimensional aspect of nano-vessels has been referred to as shape selectivity.2 The effect of spatial confinement can potentially be exerted at all points on the reaction surface but its influence on three stationary points along the reaction coordinate (reactants, transition states, and products) deserve special attention.3,4 (1) Molecular sieving of the reactants, excluding substrates of the incorrect dimension from the reaction site can occur (reactant selectivity). (2) Enzyme-like size selection or shape stabilization of transition states can dramatically influence reaction pathways (transition state selectivity). (3) Finally, products can be selectively retained that are too large to be removed via the nano-vessel openings/pores (product selectivity). 

Fig. 3.2 A schematic of a molecular potential energy curve with three stationary points two local minima (32 E/dq2 > 0) and one transition state (32 E/dq2 < 0).

Design of molecular materials with specific properties often requires interdisciplinary research involving various experimental and theoretical techniques. Molecular modeling by ab initio methods based on quantum-mechanics is now commonly used in such studies. However, theoretical investigations are still dominated by traditional, static approaches in which the stationary points on the respective potential... 

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