In statistical mechanics, configuration entropy is the portion of a system’s entropy that is related to the position of its constituent particles rather than to their velocity or momentum. It is physically related to the number of ways of arranging all the particles of the system while maintaining some overall set of specified system properties, such as energy. The configurational entropy is also known as microscopic entropy or conformational entropy in the study of macromolecules. In general, configurational entropy is the foundation of statistical thermodynamics.
The notion of configurational entropy is used a lot in one of the founding books of ID, Mystery of Life’s Origin. In some material science texts, entropy is divided into thermal and configurational entropy. I’m not so sure there is a difference between “configuration” and “configurational” entropy. Some physicists seem to not like this partitioning of entropies into thermal and configurational (as is done in material science texts).
There has been debate TSZ about whether the computation of entropy should involve position or configuration. Mike said, “if it’s not about energy, it’s not about entropy.” I disagreed, and even though Mike is far more senior than I since I’m merely a dabbler, and Mike is a professional, when I studied statistical mechanics, position was included in the calculation of entropy, and hence the importance of the Liouville theorem.
Here is an article from the entropy site from a professor of Chemistry. I think it is a balanced viewpoint:
Configurational Entropy Revisted.
Positional entropy focuses on the number of positions in space that can be occupied by the molecules of a system. Then, to the extent that more positions exist after a process than before, the greater is the entropy increase in the system. Configurational (positional) entropy has a distinguished history. Developed from classical statistical mechanics, it was the basis of Pauling’s 1935 determination of the residual entropy in ice (1), Bent’s brilliantly simple development of the entropy of mixing in 1965 (2), and more recently, such publications as Craig’s use of the cell model in presenting entropy change in mixing (3). There is no question about the correct values obtained from such calculations via configurational entropy change, the facile steps in the procedure, or its being the only practical method for calculating entropy change in some complex areas of thermodynamics.
The fact that thermal entropy (measuring changes in energy distributions) yields the same results as positional entropy (measuring numbers of positions in space) means that there is no reason that positional entropy with its usual lengthy or superficial support via probability need be presented to students in general chemistry. (There is equally no reason why professionals may not continue to use configurational entropy if it fits their preference,) Beginning students—overloaded with new material as they are and increasingly “concrete minded” rather than enjoying abstractions—should not be presented with positional entropy in general chemistry.