Entropy
From the number of accessible microstates, we can obtain the Entropy of the system via
where is the Boltzmann constant. Or, equivalently,
Some textbooks present this formula as the definition of entropy. If the entropy is defined phenomenologically via the second law of thermodynamics one has to show that the formula above indeed satisfies the law .
Notice that, for the microcanonical ensemble, plays the role of the partition function in the canonical and grand canonical ensembles. For this reason, it is also sometimes referred to as the "microcanonical partition function". We should note here that the notion of multiplicity is valid for any thermodynamical system. The same can be said for partition functions and any ensemble. It is only for the microcanonical ensemble that they happen to be the same.
is also called the characteristic state function of the microcanonical ensemble.
Read more about this topic: Microcanonical Ensemble
Famous quotes containing the word entropy:
“Just as the constant increase of entropy is the basic law of the universe, so it is the basic law of life to be ever more highly structured and to struggle against entropy.”
—Václav Havel (b. 1936)