An introduction to the potential of mean force

In this section, we will give a short introduction to some important results of this chapter, in particular, to the concept of a potential of mean force. 

For any given reaction, the rate constant according to transition-state theory (TST) is given by the average flux across the transition state (TS) from reactants to products. Denoting the reaction coordinate by qi and the TS by qand asserting (arbitrarily) 

To obtain a simplified expression for tst, it is convenient to make a coordinate transformation to a set of coordinates that includes the reaction coordinate  

Such a transformation will typically be a transformation to normal-mode coordinates around the TS for the activated complex leaving the solvent coordinates unchanged (see Sections 10.2.1 and 10.2.2 for details). This implies that 

The first term in this expression, as we have seen several times in Chapters 5 and 6, is easily evaluated  

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