Free energy relationships

The introduction to this book stressed that “matching experiments” should not be the final goal of a computational effort. To engineer better catalysts, processes, or materials, it is often more important to identify reliable ways of controlling the kinetics. This chapter explores relationships, some empirical and some derived, between kinetics and driving forces. These relationships are useful for predicting trends, e.g. how a change in solvent will change the rate of a chemical reaction, or how a mechanical pulling force will accelerate the unfolding of a protein. The relationships are also useful for interpreting kinetic trends in terms of transition state properties. For example, some free energy relationships indicate the location of a transition state, or the size of a critical nucleus, both from measurable quantities.