Free-energy calculations - Theoretical Biophysics Group

Free-energy perturbation calculations “Alchemical transformations”
The concept of order parameter is central to free energy
calculations: They are collective variables used to describe
transformations from the initial, reference system
to the final, target one.
An order parameter may, albeit does not necessarily
have to correspond to the path along which the transformation
takes place in nature, and would be called the
reaction coordinate or the reaction path if such were the
case.
There is more than one way to define an order parameter.
How to make the best, or at least an appropriate, choice
of an order parameter?
The choice of order parameters may have a significant
effect on the efficiency and accuracy of free energy calculations.
Some order parameters may map a smooth
path between the reference and target states whereas
others may lead through a rough energy landscape.
Chris Chipot Free-energy calculations