Canonical Partition Function
A "Canonical Partition Function" applies to a canonical ensemble, in which the system is allowed to exchange heat with the environment at fixed temperature, volume, and number of particles.
Applicable units are those of quantitykind:CanonicalPartitionFunction
http://en.wikipedia.org/wiki/Partition_function_(statistical_mechanics)
A "Canonical Partition Function" applies to a canonical ensemble, in which the system is allowed to exchange heat with the environment at fixed temperature, volume, and number of particles.
$Z = \sum_r e^{-\frac{E_r}{kT}}$, where the sum is over all quantum states consistent with given energy, volume, external fields, and content, $E_r$ is the energy in the $rth$ quantum state, $k$ is the Boltzmann constant, and $T$ is thermodynamic temperature.
http://www.iso.org/iso/catalogue_detail?csnumber=31894