Rapid calculation of partition functions and free energies of fluids

Hainam Do, Jonathan D. Hirst, Richard J. Wheatley

Research output: Journal PublicationArticlepeer-review

28 Citations (Scopus)


The partition function (Q) is a central quantity in statistical mechanics. All the thermodynamic properties can be derived from it. Here we show how the partition function of fluids can be calculated directly from simulations; this allows us to obtain the Helmholtz free energy (F) via F-kBT ln Q. In our approach, we divide the density of states, assigning half of the configurations found in a simulation to a high-energy partition and half to a low-energy partition. By recursively dividing the low-energy partition into halves, we map out the complete density of states for a continuous system. The result allows free energy to be calculated directly as a function of temperature. We illustrate our method in the context of the free energy of water.

Original languageEnglish
Article number174105
JournalJournal of Chemical Physics
Issue number17
Publication statusPublished - 7 Nov 2011
Externally publishedYes

ASJC Scopus subject areas

  • Physics and Astronomy (all)
  • Physical and Theoretical Chemistry


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